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/*
* Copyright (C) 2019 The Android Open Source Project
*
* 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.google.android.setupcompat.internal;
import android.os.Looper;
/**
* Static convenience methods that help a method or constructor check whether it was invoked
* correctly (that is, whether its <i>preconditions</i> were met).
*
* <p>If the precondition is not met, the {@code Preconditions} method throws an unchecked exception
* of a specified type, which helps the method in which the exception was thrown communicate that
* its caller has made a mistake.
*/
public final class Preconditions {
/** Ensures the truth of an expression involving one or more parameters to the calling method. */
public static void checkArgument(boolean expression, String errorMessage) {
if (!expression) {
throw new IllegalArgumentException(errorMessage);
}
}
/**
* Ensures the truth of an expression involving the state of the calling instance, but not
* involving any parameters to the calling method.
*/
public static void checkState(boolean expression, String errorMessage) {
if (!expression) {
throw new IllegalStateException(errorMessage);
}
}
/** Ensures that an object reference passed as a parameter to the calling method is not null. */
public static <T> T checkNotNull(T reference, String errorMessage) {
if (reference == null) {
throw new NullPointerException(errorMessage);
}
return reference;
}
/**
* Ensures that this method is called from the main thread, otherwise an exception will be thrown.
*/
public static void ensureOnMainThread(String whichMethod) {
if (Looper.myLooper() == Looper.getMainLooper()) {
return;
}
throw new IllegalStateException(whichMethod + " must be called from the UI thread.");
}
}
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