Preconditions.java
/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.cronutils.utils;
import java.util.Collection;
/**
*
* <h2></h2> Due to: https://bugs.openjdk.java.net/browse/JDK-8219801
*
* Static convenience methods that help a method or constructor check whether it was invoked.
* correctly (whether its <i>preconditions</i> have been met). These methods generally accept a
* {@code boolean} expression which is expected to be {@code true} (or in the case of {@code
* checkNotNull}, an object reference which is expected to be non-null). When {@code false} (or
* {@code null}) is passed instead, the {@code Preconditions} method throws an unchecked exception,
* which helps the calling method communicate to <i>its</i> caller that <i>that</i> caller has made
* a mistake. Example: <pre> {@code
*
* /**
* * Returns the positive square root of the given value.
* *
* * @throws IllegalArgumentException if the value is negative
* *}{@code /
* public static double sqrt(double value) {
* Preconditions.checkArgument(value >= 0.0, "negative value: %s", value);
* // calculate the square root
* }
*
* void exampleBadCaller() {
* double d = sqrt(-1.0);
* }}</pre>
*
* <p>In this example, {@code checkArgument} throws an {@code IllegalArgumentException} to indicate
* that {@code exampleBadCaller} made an error in <i>its</i> call to {@code sqrt}.
*
* <h3>Warning about performance</h3>
*
* <p>The goal of this class is to improve readability of code, but in some circumstances this may
* come at a significant performance cost. Remember that parameter values for message construction
* must all be computed eagerly, and autoboxing and varargs array creation may happen as well, even
* when the precondition check then succeeds (as it should almost always do in production). In some
* circumstances these wasted CPU cycles and allocations can add up to a real problem.
* Performance-sensitive precondition checks can always be converted to the customary form:
* <pre> {@code
*
* if (value < 0.0) {
* throw new IllegalArgumentException("negative value: " + value);
* }}</pre>
*
* <h3>Other types of preconditions</h3>
*
* <p>Not every type of precondition failure is supported by these methods. Continue to throw
* standard JDK exceptions such as {@link java.util.NoSuchElementException} or {@link
* UnsupportedOperationException} in the situations they are intended for.
*
* <h3>Non-preconditions</h3>
*
* <p>It is of course possible to use the methods of this class to check for invalid conditions
* which are <i>not the caller's fault</i>. Doing so is <b>not recommended</b> because it is
* misleading to future readers of the code and of stack traces. See
* <a href="http://code.google.com/p/guava-libraries/wiki/ConditionalFailuresExplained">Conditional
* failures explained</a> in the Guava User Guide for more advice.
*
* <h3>{@code java.util.Objects.requireNonNull()}</h3>
*
* <p>Projects which use {@code com.google.common} should generally avoid the use of {@link
* java.util.Objects#requireNonNull(Object)}. Instead, use whichever of {@link
* #checkNotNull(Object)} or Verify#verifyNotNull(Object) is appropriate to the situation.
* (The same goes for the message-accepting overloads.)
*
* <h3>Only {@code %s} is supported</h3>
*
* <p>In {@code Preconditions} error message template strings, only the {@code "%s"} specifier is
* supported, not the full range of {@link java.util.Formatter} specifiers.
*
* <h3>More information</h3>
*
* <p>See the Guava User Guide on
* <a href="http://code.google.com/p/guava-libraries/wiki/PreconditionsExplained">using {@code
* Preconditions}</a>.
*
* @author Kevin Bourrillion
* @since 2.0 (imported from Google Collections Library)
*/
public class Preconditions {
private Preconditions() {}
/**
* Ensures the truth of an expression involving one or more parameters to the calling method.
*
* @param expression a boolean expression
* @param errorMessage the exception message to use if the check fails; will be converted to a
* string using {@link String#valueOf(Object)}
* @throws IllegalArgumentException if {@code expression} is false
*/
public static void checkArgument(final boolean expression, final Object errorMessage) {
if (!expression) {
throw new IllegalArgumentException(String.valueOf(errorMessage));
}
}
public static void checkPositive(final int value, final Object errorMessage) {
if (value < 0) {
throw new IllegalArgumentException(String.valueOf(errorMessage));
}
}
/**
* Ensures the truth of an expression involving one or more parameters to the calling method.
*
* @param expression a boolean expression
* @param errorMessageTemplate a template for the exception message should the check fail. The
* message is formed by replacing each {@code %s} placeholder in the template with an
* argument. These are matched by position - the first {@code %s} gets {@code
* errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message
* in square braces. Unmatched placeholders will be left as-is.
* @param errorMessageArgs the arguments to be substituted into the message template. Arguments
* are converted to strings using {@link String#valueOf(Object)}.
* @throws IllegalArgumentException if {@code expression} is false
* @throws NullPointerException if the check fails and either {@code errorMessageTemplate} or
* {@code errorMessageArgs} is null (don't let this happen)
*/
public static void checkArgument(final boolean expression,
final String errorMessageTemplate,
final Object... errorMessageArgs) {
if (!expression) {
throw new IllegalArgumentException(format(errorMessageTemplate, errorMessageArgs));
}
}
/**
* Ensures the truth of an expression involving the state of the calling instance, but not.
* involving any parameters to the calling method.
*
* @param expression a boolean expression
* @param errorMessageTemplate a template for the exception message should the check fail. The
* message is formed by replacing each {@code %s} placeholder in the template with an
* argument. These are matched by position - the first {@code %s} gets {@code
* errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message
* in square braces. Unmatched placeholders will be left as-is.
* @param errorMessageArgs the arguments to be substituted into the message template. Arguments
* are converted to strings using {@link String#valueOf(Object)}.
* @throws IllegalStateException if {@code expression} is false
* @throws NullPointerException if the check fails and either {@code errorMessageTemplate} or
* {@code errorMessageArgs} is null (don't let this happen)
*/
public static void checkState(final boolean expression,
final String errorMessageTemplate,
final Object... errorMessageArgs) {
if (!expression) {
throw new IllegalStateException(format(errorMessageTemplate, errorMessageArgs));
}
}
/**
* Ensures that an object reference passed as a parameter to the calling method is not null.
*
* @param reference an object reference
* @return T - the non-null reference that was validated
* @throws NullPointerException if {@code reference} is null
*/
public static <T> T checkNotNull(final T reference) {
if (reference == null) {
throw new NullPointerException();
}
return reference;
}
/**
* Ensures that an object reference passed as a parameter to the calling method is not null.
*
* @param reference an object reference
* @param errorMessage the exception message to use if the check fails; will be converted to a
* string using {@link String#valueOf(Object)}
* @return the non-null reference that was validated
* @throws NullPointerException if {@code reference} is null
*/
@SuppressWarnings(value = "NullPointerException")
public static <T> T checkNotNull(final T reference, final Object errorMessage) {
if (reference == null) {
throw new NullPointerException(String.valueOf(errorMessage));
}
return reference;
}
/**
* Ensures that a string reference passed as a parameter to the calling method is not null.
* nor empty.
*
* @param reference a string reference
* @param errorMessage the exception message to use if the check fails; will be converted to a
* string using {@link String#valueOf(Object)}
* @return the non-null reference that was validated
* @throws NullPointerException if {@code reference} is null
* @throws IllegalArgumentException if {@code reference} is empty
*/
public static String checkNotNullNorEmpty(final String reference, final Object errorMessage) {
if (reference == null) {
throw new NullPointerException(String.valueOf(errorMessage));
}
if (reference.isEmpty()) {
throw new IllegalArgumentException(String.valueOf(errorMessage));
}
return reference;
}
/**
* Ensures that a collection reference passed as a parameter to the calling method is not null.
* nor empty.
*
* @param reference a collection reference
* @param errorMessage the exception message to use if the check fails; will be converted to a
* string using {@link String#valueOf(Object)}
* @return the non-null reference that was validated
* @throws NullPointerException if {@code reference} is null
* @throws IllegalArgumentException if {@code reference} is empty
*/
public static <T extends Collection<?>> T checkNotNullNorEmpty(final T reference, final Object errorMessage) {
if (reference == null) {
throw new NullPointerException(String.valueOf(errorMessage));
}
if (reference.isEmpty()) {
throw new IllegalArgumentException(String.valueOf(errorMessage));
}
return reference;
}
/**
* Substitutes each {@code %s} in {@code template} with an argument. These are matched by
* position: the first {@code %s} gets {@code args[0]}, etc. If there are more arguments than
* placeholders, the unmatched arguments will be appended to the end of the formatted message in
* square braces.
*
* @param nullableTemplate a non-null string containing 0 or more {@code %s} placeholders.
* @param args the arguments to be substituted into the message template. Arguments are converted
* to strings using {@link String#valueOf(Object)}. Arguments can be null.
*/
// Note that this is somewhat-improperly used from Verify.java as well.
private static String format(final String nullableTemplate, final Object... args) {
final String template = String.valueOf(nullableTemplate); // null -> "null"
// start substituting the arguments into the '%s' placeholders
final StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
int templateStart = 0;
int i = 0;
while (i < args.length) {
final int placeholderStart = template.indexOf("%s", templateStart);
if (placeholderStart == -1) {
break;
}
builder.append(template.substring(templateStart, placeholderStart));
builder.append(args[i++]);
templateStart = placeholderStart + 2;
}
builder.append(template.substring(templateStart));
// if we run out of placeholders, append the extra args in square braces
if (i < args.length) {
builder.append(" [");
builder.append(args[i++]);
while (i < args.length) {
builder.append(", ");
builder.append(args[i++]);
}
builder.append(']');
}
return builder.toString();
}
}