440 lines
19 KiB
Plaintext
440 lines
19 KiB
Plaintext
/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
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* in compliance with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the License
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* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the License for the specific language governing permissions and limitations under
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* the License.
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*/
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package com.ifish.jpush.utils;
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/**
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* Copied from Google Guava.
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*
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* Static convenience methods that help a method or constructor check whether it was invoked
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* correctly (whether its <i>preconditions</i> have been met). These methods generally accept a
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* {@code boolean} expression which is expected to be {@code true} (or in the case of {@code
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* checkNotNull}, an object reference which is expected to be non-null). When {@code false} (or
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* {@code null}) is passed instead, the {@code Preconditions} method throws an unchecked exception,
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* which helps the calling method communicate to <i>its</i> caller that <i>that</i> caller has made
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* a mistake. Example: <pre> {@code
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*
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* /**
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* * Returns the positive square root of the given value.
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* *
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* * @throws IllegalArgumentException if the value is negative
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* *}{@code /
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* public static double sqrt(double value) {
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* Preconditions.checkArgument(value >= 0.0, "negative value: %s", value);
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* // calculate the square root
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* }
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*
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* void exampleBadCaller() {
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* double d = sqrt(-1.0);
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* }}</pre>
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*
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* In this example, {@code checkArgument} throws an {@code IllegalArgumentException} to indicate
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* that {@code exampleBadCaller} made an error in <i>its</i> call to {@code sqrt}.
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*
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* <h3>Warning about performance</h3>
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*
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* <p>The goal of this class is to improve readability of code, but in some circumstances this may
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* come at a significant performance cost. Remember that parameter values for message construction
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* must all be computed eagerly, and autoboxing and varargs array creation may happen as well, even
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* when the precondition check then succeeds (as it should almost always do in production). In some
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* circumstances these wasted CPU cycles and allocations can add up to a real problem.
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* Performance-sensitive precondition checks can always be converted to the customary form:
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* <pre> {@code
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*
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* if (value < 0.0) {
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* throw new IllegalArgumentException("negative value: " + value);
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* }}</pre>
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*
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* <h3>Other types of preconditions</h3>
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*
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* <p>Not every type of precondition failure is supported by these methods. Continue to throw
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* standard JDK exceptions such as {@link java.util.NoSuchElementException} or {@link
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* UnsupportedOperationException} in the situations they are intended for.
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*
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* <h3>Non-preconditions</h3>
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*
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* <p>It is of course possible to use the methods of this class to check for invalid conditions
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* which are <i>not the caller's fault</i>. Doing so is <b>not recommended</b> because it is
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* misleading to future readers of the code and of stack traces. See
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* <a href="http://code.google.com/p/guava-libraries/wiki/ConditionalFailuresExplained">Conditional
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* failures explained</a> in the Guava User Guide for more advice.
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*
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* <h3>{@code java.util.Objects.requireNonNull()}</h3>
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*
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* <p>Projects which use {@code com.google.common} should generally avoid the use of {@link
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* java.util.Objects#requireNonNull(Object)}. Instead, use whichever of {@link
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* #checkNotNull(Object)} or {@link Verify#verifyNotNull(Object)} is appropriate to the situation.
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* (The same goes for the message-accepting overloads.)
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*
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* <h3>Only {@code %s} is supported</h3>
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*
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* <p>In {@code Preconditions} error message template strings, only the {@code "%s"} specifier is
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* supported, not the full range of {@link java.util.Formatter} specifiers. However, note that if
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* the number of arguments does not match the number of occurrences of {@code "%s"} in the format
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* string, {@code Preconditions} will still behave as expected, and will still include all argument
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* values in the error message; the message will simply not be formatted exactly as intended.
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*
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* <h3>More information</h3>
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*
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* <p>See the Guava User Guide on
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* <a href="http://code.google.com/p/guava-libraries/wiki/PreconditionsExplained">using {@code
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* Preconditions}</a>.
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*
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* @author Kevin Bourrillion
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* @since 2.0 (imported from Google Collections Library)
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*/
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public final class Preconditions {
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private Preconditions() {}
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/**
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* Ensures the truth of an expression involving one or more parameters to the calling method.
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*
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* @param expression a boolean expression
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* @throws IllegalArgumentException if {@code expression} is false
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*/
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public static void checkArgument(boolean expression) {
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if (!expression) {
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throw new IllegalArgumentException();
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}
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}
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/**
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* Ensures the truth of an expression involving one or more parameters to the calling method.
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*
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* @param expression a boolean expression
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* @param errorMessage the exception message to use if the check fails; will be converted to a
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* string using {@link String#valueOf(Object)}
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* @throws IllegalArgumentException if {@code expression} is false
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*/
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public static void checkArgument(boolean expression, @Nullable Object errorMessage) {
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if (!expression) {
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throw new IllegalArgumentException(String.valueOf(errorMessage));
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}
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}
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/**
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* Ensures the truth of an expression involving one or more parameters to the calling method.
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*
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* @param expression a boolean expression
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* @param errorMessageTemplate a template for the exception message should the check fail. The
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* message is formed by replacing each {@code %s} placeholder in the template with an
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* argument. These are matched by position - the first {@code %s} gets {@code
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* errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message
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* in square braces. Unmatched placeholders will be left as-is.
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* @param errorMessageArgs the arguments to be substituted into the message template. Arguments
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* are converted to strings using {@link String#valueOf(Object)}.
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* @throws IllegalArgumentException if {@code expression} is false
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* @throws NullPointerException if the check fails and either {@code errorMessageTemplate} or
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* {@code errorMessageArgs} is null (don't let this happen)
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*/
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public static void checkArgument(boolean expression,
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@Nullable String errorMessageTemplate,
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@Nullable Object... errorMessageArgs) {
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if (!expression) {
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throw new IllegalArgumentException(format(errorMessageTemplate, errorMessageArgs));
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}
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}
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/**
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* Ensures the truth of an expression involving the state of the calling instance, but not
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* involving any parameters to the calling method.
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*
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* @param expression a boolean expression
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* @throws IllegalStateException if {@code expression} is false
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*/
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public static void checkState(boolean expression) {
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if (!expression) {
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throw new IllegalStateException();
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}
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}
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/**
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* Ensures the truth of an expression involving the state of the calling instance, but not
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* involving any parameters to the calling method.
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*
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* @param expression a boolean expression
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* @param errorMessage the exception message to use if the check fails; will be converted to a
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* string using {@link String#valueOf(Object)}
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* @throws IllegalStateException if {@code expression} is false
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*/
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public static void checkState(boolean expression, @Nullable Object errorMessage) {
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if (!expression) {
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throw new IllegalStateException(String.valueOf(errorMessage));
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}
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}
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/**
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* Ensures the truth of an expression involving the state of the calling instance, but not
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* involving any parameters to the calling method.
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*
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* @param expression a boolean expression
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* @param errorMessageTemplate a template for the exception message should the check fail. The
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* message is formed by replacing each {@code %s} placeholder in the template with an
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* argument. These are matched by position - the first {@code %s} gets {@code
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* errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message
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* in square braces. Unmatched placeholders will be left as-is.
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* @param errorMessageArgs the arguments to be substituted into the message template. Arguments
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* are converted to strings using {@link String#valueOf(Object)}.
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* @throws IllegalStateException if {@code expression} is false
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* @throws NullPointerException if the check fails and either {@code errorMessageTemplate} or
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* {@code errorMessageArgs} is null (don't let this happen)
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*/
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public static void checkState(boolean expression,
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@Nullable String errorMessageTemplate,
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@Nullable Object... errorMessageArgs) {
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if (!expression) {
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throw new IllegalStateException(format(errorMessageTemplate, errorMessageArgs));
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}
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}
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/**
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* Ensures that an object reference passed as a parameter to the calling method is not null.
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*
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* @param reference an object reference
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* @return the non-null reference that was validated
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* @throws NullPointerException if {@code reference} is null
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*/
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public static <T> T checkNotNull(T reference) {
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if (reference == null) {
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throw new NullPointerException();
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}
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return reference;
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}
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/**
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* Ensures that an object reference passed as a parameter to the calling method is not null.
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*
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* @param reference an object reference
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* @param errorMessage the exception message to use if the check fails; will be converted to a
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* string using {@link String#valueOf(Object)}
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* @return the non-null reference that was validated
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* @throws NullPointerException if {@code reference} is null
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*/
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public static <T> T checkNotNull(T reference, @Nullable Object errorMessage) {
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if (reference == null) {
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throw new NullPointerException(String.valueOf(errorMessage));
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}
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return reference;
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}
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/**
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* Ensures that an object reference passed as a parameter to the calling method is not null.
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*
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* @param reference an object reference
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* @param errorMessageTemplate a template for the exception message should the check fail. The
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* message is formed by replacing each {@code %s} placeholder in the template with an
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* argument. These are matched by position - the first {@code %s} gets {@code
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* errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message
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* in square braces. Unmatched placeholders will be left as-is.
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* @param errorMessageArgs the arguments to be substituted into the message template. Arguments
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* are converted to strings using {@link String#valueOf(Object)}.
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* @return the non-null reference that was validated
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* @throws NullPointerException if {@code reference} is null
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*/
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public static <T> T checkNotNull(T reference,
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@Nullable String errorMessageTemplate,
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@Nullable Object... errorMessageArgs) {
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if (reference == null) {
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// If either of these parameters is null, the right thing happens anyway
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throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
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}
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return reference;
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}
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/*
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* All recent hotspots (as of 2009) *really* like to have the natural code
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*
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* if (guardExpression) {
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* throw new BadException(messageExpression);
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* }
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*
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* refactored so that messageExpression is moved to a separate String-returning method.
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*
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* if (guardExpression) {
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* throw new BadException(badMsg(...));
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* }
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*
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* The alternative natural refactorings into void or Exception-returning methods are much slower.
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* This is a big deal - we're talking factors of 2-8 in microbenchmarks, not just 10-20%. (This
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* is a hotspot optimizer bug, which should be fixed, but that's a separate, big project).
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*
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* The coding pattern above is heavily used in java.util, e.g. in ArrayList. There is a
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* RangeCheckMicroBenchmark in the JDK that was used to test this.
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*
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* But the methods in this class want to throw different exceptions, depending on the args, so it
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* appears that this pattern is not directly applicable. But we can use the ridiculous, devious
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* trick of throwing an exception in the middle of the construction of another exception. Hotspot
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* is fine with that.
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*/
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/**
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* Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size
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* {@code size}. An element index may range from zero, inclusive, to {@code size}, exclusive.
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*
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* @param index a user-supplied index identifying an element of an array, list or string
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* @param size the size of that array, list or string
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* @return the value of {@code index}
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* @throws IndexOutOfBoundsException if {@code index} is negative or is not less than {@code size}
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* @throws IllegalArgumentException if {@code size} is negative
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*/
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public static int checkElementIndex(int index, int size) {
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return checkElementIndex(index, size, "index");
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}
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/**
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* Ensures that {@code index} specifies a valid <i>element</i> in an array, list or string of size
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* {@code size}. An element index may range from zero, inclusive, to {@code size}, exclusive.
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*
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* @param index a user-supplied index identifying an element of an array, list or string
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* @param size the size of that array, list or string
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* @param desc the text to use to describe this index in an error message
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* @return the value of {@code index}
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* @throws IndexOutOfBoundsException if {@code index} is negative or is not less than {@code size}
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* @throws IllegalArgumentException if {@code size} is negative
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*/
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public static int checkElementIndex(
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int index, int size, @Nullable String desc) {
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// Carefully optimized for execution by hotspot (explanatory comment above)
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if (index < 0 || index >= size) {
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throw new IndexOutOfBoundsException(badElementIndex(index, size, desc));
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}
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return index;
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}
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private static String badElementIndex(int index, int size, String desc) {
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if (index < 0) {
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return format("%s (%s) must not be negative", desc, index);
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} else if (size < 0) {
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throw new IllegalArgumentException("negative size: " + size);
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} else { // index >= size
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return format("%s (%s) must be less than size (%s)", desc, index, size);
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}
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}
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/**
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* Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of
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* size {@code size}. A position index may range from zero to {@code size}, inclusive.
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*
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* @param index a user-supplied index identifying a position in an array, list or string
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* @param size the size of that array, list or string
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* @return the value of {@code index}
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* @throws IndexOutOfBoundsException if {@code index} is negative or is greater than {@code size}
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* @throws IllegalArgumentException if {@code size} is negative
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*/
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public static int checkPositionIndex(int index, int size) {
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return checkPositionIndex(index, size, "index");
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}
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/**
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* Ensures that {@code index} specifies a valid <i>position</i> in an array, list or string of
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* size {@code size}. A position index may range from zero to {@code size}, inclusive.
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*
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* @param index a user-supplied index identifying a position in an array, list or string
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* @param size the size of that array, list or string
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* @param desc the text to use to describe this index in an error message
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* @return the value of {@code index}
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* @throws IndexOutOfBoundsException if {@code index} is negative or is greater than {@code size}
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* @throws IllegalArgumentException if {@code size} is negative
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*/
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public static int checkPositionIndex(int index, int size, @Nullable String desc) {
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// Carefully optimized for execution by hotspot (explanatory comment above)
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if (index < 0 || index > size) {
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throw new IndexOutOfBoundsException(badPositionIndex(index, size, desc));
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}
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return index;
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}
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private static String badPositionIndex(int index, int size, String desc) {
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if (index < 0) {
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return format("%s (%s) must not be negative", desc, index);
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} else if (size < 0) {
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throw new IllegalArgumentException("negative size: " + size);
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} else { // index > size
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return format("%s (%s) must not be greater than size (%s)", desc, index, size);
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}
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}
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/**
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* Ensures that {@code start} and {@code end} specify a valid <i>positions</i> in an array, list
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* or string of size {@code size}, and are in order. A position index may range from zero to
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* {@code size}, inclusive.
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*
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* @param start a user-supplied index identifying a starting position in an array, list or string
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* @param end a user-supplied index identifying a ending position in an array, list or string
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* @param size the size of that array, list or string
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* @throws IndexOutOfBoundsException if either index is negative or is greater than {@code size},
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* or if {@code end} is less than {@code start}
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* @throws IllegalArgumentException if {@code size} is negative
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*/
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public static void checkPositionIndexes(int start, int end, int size) {
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// Carefully optimized for execution by hotspot (explanatory comment above)
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if (start < 0 || end < start || end > size) {
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throw new IndexOutOfBoundsException(badPositionIndexes(start, end, size));
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}
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}
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private static String badPositionIndexes(int start, int end, int size) {
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if (start < 0 || start > size) {
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return badPositionIndex(start, size, "start index");
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}
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if (end < 0 || end > size) {
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return badPositionIndex(end, size, "end index");
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}
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// end < start
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return format("end index (%s) must not be less than start index (%s)", end, start);
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}
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/**
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* Substitutes each {@code %s} in {@code template} with an argument. These are matched by
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* position: the first {@code %s} gets {@code args[0]}, etc. If there are more arguments than
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* placeholders, the unmatched arguments will be appended to the end of the formatted message in
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* square braces.
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*
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* @param template a non-null string containing 0 or more {@code %s} placeholders.
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* @param args the arguments to be substituted into the message template. Arguments are converted
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* to strings using {@link String#valueOf(Object)}. Arguments can be null.
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*/
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// Note that this is somewhat-improperly used from Verify.java as well.
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static String format(String template, @Nullable Object... args) {
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template = String.valueOf(template); // null -> "null"
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// start substituting the arguments into the '%s' placeholders
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StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
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int templateStart = 0;
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int i = 0;
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while (i < args.length) {
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int placeholderStart = template.indexOf("%s", templateStart);
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if (placeholderStart == -1) {
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break;
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}
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builder.append(template.substring(templateStart, placeholderStart));
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builder.append(args[i++]);
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templateStart = placeholderStart + 2;
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}
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builder.append(template.substring(templateStart));
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// if we run out of placeholders, append the extra args in square braces
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if (i < args.length) {
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builder.append(" [");
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builder.append(args[i++]);
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while (i < args.length) {
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builder.append(", ");
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builder.append(args[i++]);
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}
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builder.append(']');
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}
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return builder.toString();
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}
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}
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