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/*
* Copyright (c) 2009-2013 JGoodies Software GmbH. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* o Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* o Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* o Neither the name of JGoodies Software GmbH nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.privatejgoodies.common.base;
import java.util.Formatter;
/**
* Reduces the code necessary to check preconditions on method state and parameters.
*
* @author Karsten Lentzsch
*/
public final class Preconditions {
private Preconditions() {
// Override default constructor; prevents instantiation.
}
// Tests that throw IllegalArgumentExceptions *****************************
/**
* Checks the truth of the given expression and throws a customized
* {@link IllegalArgumentException} if it is false. Intended for doing parameter validation in
* methods and constructors, e.g.:
*
* public void foo(int count) {
* Preconditions.checkArgument(count > 0, "count must be positive.");
* }
*
*
* @param expression the precondition to check involving one ore more parameters to the calling
* method or constructor
* @param message the detail message to be used in the event that an exception is thrown
* @throws IllegalArgumentException if {@code expression} is false
*/
public static void checkArgument(boolean expression, String message) {
if (!expression) {
throw new IllegalArgumentException(message);
}
}
/**
* Checks the truth of the given expression and throws a customized
* {@link IllegalArgumentException} if it is false. Intended for doing parameter validation in
* methods and constructors, e.g.:
*
* public void foo(int count) {
* Preconditions.checkArgument(count > 0, "count must be positive: %s.", count);
* }
*
*
* @param expression the precondition to check involving one ore more parameters to the calling
* method or constructor
* @param messageFormat a {@link Formatter format} string for the detail message to be used in
* the event that an exception is thrown.
* @param messageArgs the arguments referenced by the format specifiers in the
* {@code messageFormat}
* @throws IllegalArgumentException if {@code expression} is false
*/
public static void checkArgument(
boolean expression, String messageFormat, Object... messageArgs) {
if (!expression) {
throw new IllegalArgumentException(format(messageFormat, messageArgs));
}
}
// Tests Throwing NullPointerExceptions ***********************************
/**
* Checks that the given object reference is not {@code null} and throws a customized
* {@link NullPointerException} if it is. Intended for doing parameter validation in methods and
* constructors, e.g.:
*
* public void foo(Bar bar, Baz baz) {
* this.bar = Preconditions.checkNotNull(bar, "bar must not be null.");
* Preconditions.checkNotBull(baz, "baz must not be null.");
* }
*
*
* @param reference the object reference to check for being {@code null}
* @param message the detail message to be used in the event that an exception is thrown
* @param the type of the reference
* @return {@code reference} if not {@code null}
* @throws NullPointerException if {@code reference} is {@code null}
*/
public static T checkNotNull(T reference, String message) {
if (reference == null) {
throw new NullPointerException(message);
}
return reference;
}
/**
* Checks that the given object reference is not {@code null} and throws a customized
* {@link NullPointerException} if it is. Intended for doing parameter validation in methods and
* constructors, e.g.:
*
* public void foo(Bar bar, Baz baz) {
* this.bar = Preconditions.checkNotNull(bar, "bar must not be null.");
* Preconditions.checkNotBull(baz, "The %s must not be null.", "baz");
* }
*
*
* @param reference the object reference to check for being {@code null}
* @param messageFormat a {@link Formatter format} string for the detail message to be used in
* the event that an exception is thrown.
* @param messageArgs the arguments referenced by the format specifiers in the
* {@code messageFormat}
* @param the type of the reference
* @return {@code reference} if not {@code null}
* @throws NullPointerException if {@code reference} is {@code null}
*/
public static T checkNotNull(
T reference, String messageFormat, Object... messageArgs) {
if (reference == null) {
throw new NullPointerException(format(messageFormat, messageArgs));
}
return reference;
}
// Tests Throwing IllegalStateExceptions **********************************
/**
* Checks the truth of the given expression and throws a customized
* {@link IllegalStateException} if it is false. Intended for doing validation in methods
* involving the state of the calling instance, but not involving parameters of the calling
* method, e.g.:
*
* public void unlock() {
* Preconditions.checkState(locked, "Must be locked to be unlocked.");
* }
*
*
* @param expression the precondition to check involving the state of the calling instance
* @param message the detail message to be used in the event that an exception is thrown
* @throws IllegalStateException if {@code expression} is false
*/
public static void checkState(boolean expression, String message) {
if (!expression) {
throw new IllegalStateException(message);
}
}
/**
* Checks the truth of the given expression and throws a customized
* {@link IllegalStateException} if it is false. Intended for doing validation in methods
* involving the state of the calling instance, but not involving parameters of the calling
* method, e.g.:
*
* public void unlock() {
* Preconditions.checkState(locked,
* "Must be locked to be unlocked. Most recent lock: %s",
* mostRecentLock);
* }
*
*
* @param expression the precondition to check involving the state of the calling instance
* @param messageFormat a {@link Formatter format} string for the detail message to be used in
* the event that an exception is thrown.
* @param messageArgs the arguments referenced by the format specifiers in the
* {@code messageFormat}
* @throws IllegalStateException if {@code expression} is false
*/
public static void checkState(
boolean expression, String messageFormat, Object... messageArgs) {
if (!expression) {
throw new IllegalStateException(format(messageFormat, messageArgs));
}
}
// Combined Tests Throwing Multiple Exceptions ****************************
/**
* Checks that the given string is not blank and throws a customized
* {@link NullPointerException} if it is {@code null}, and a customized
* {@link IllegalArgumentException} if it is empty or whitespace. Intended for doing parameter
* validation in methods and constructors, e.g.:
*
* public void foo(String text) {
* checkNotBlank(text, "The text must not be null, empty or whitespace.");
* }
*
*
* @param str the string to check for being blank
* @param message the detail message to be used in the event that an exception is thrown
* @return {@code str} if not {@code null}
* @throws NullPointerException if {@code str} is {@code null}
* @throws IllegalArgumentException if {@code str} is empty or whitespace
*/
public static String checkNotBlank(String str, String message) {
checkNotNull(str, message);
checkArgument(Strings.isNotBlank(str), message);
return str;
}
/**
* Checks that the given string is not blank and throws a customized
* {@link NullPointerException} if it is {@code null}, and a customized
* {@link IllegalArgumentException} if it is empty or whitespace. Intended for doing parameter
* validation in methods and constructors, e.g.:
*
* public void foo(String text, String id) {
* checkNotBlank(
* text,
* "The text for %s must not be null, empty or whitespace.",
* id);
* }
*
*
* @param str the string to check for being blank
* @param messageFormat a {@link Formatter format} string for the detail message to be used in
* the event that an exception is thrown.
* @param messageArgs the arguments referenced by the format specifiers in the
* {@code messageFormat}
* @return {@code str} if not {@code null}
* @throws NullPointerException if {@code str} is {@code null}
* @throws IllegalArgumentException if {@code str} is empty or whitespace
*/
public static String checkNotBlank(
String str, String messageFormat, Object... messageArgs) {
checkNotNull(str, messageFormat, messageArgs);
checkArgument(Strings.isNotBlank(str), messageFormat, messageArgs);
return str;
}
// Helper Code ************************************************************
static String format(String messageFormat, Object... messageArgs) {
return String.format(messageFormat, messageArgs);
}
}
