runner/src/main/java/android/support/test/internal/util/Checks.java

/*
 * Copyright (C) 2014 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 android.support.test.internal.util;

import android.os.Looper;

/**
 * Utility method for checking for null references
 */
public final class Checks {

    private Checks() {
    }

    public static <T> T checkNotNull(T reference) {
        if (reference == null) {
            throw new NullPointerException();
        }
        return reference;
    }

    public static <T> T checkNotNull(T reference, Object errorMessage) {
        if (reference == null) {
            throw new NullPointerException(String.valueOf(errorMessage));
        }
        return reference;
    }

    public static <T> T checkNotNull(T reference,
            String errorMessageTemplate,
            Object... errorMessageArgs) {
        if (reference == null) {
            // If either of these parameters is null, the right thing happens
            // anyway
            throw new NullPointerException(
                    format(errorMessageTemplate, errorMessageArgs));
        }
        return reference;
    }

    public static void checkState(boolean expression) {
        if (!expression) {
            throw new IllegalStateException();
        }
    }

    public static void checkState(
            boolean expression, Object errorMessage) {
        if (!expression) {
            throw new IllegalStateException(String.valueOf(errorMessage));
        }
    }

    public static void checkState(boolean expression,
            String errorMessageTemplate,
            Object... errorMessageArgs) {
        if (!expression) {
            throw new IllegalStateException(
                    format(errorMessageTemplate, errorMessageArgs));
        }
    }

    /**
     * Checks if the current thread is the main thread, otherwise throws.
     *
     * @throws IllegalStateException if current thread is not the main thread.
     */
    public static void checkMainThread() {
        checkState(Thread.currentThread().equals(Looper.getMainLooper().getThread()),
                "Method cannot be called off the main application thread (on: %s)",
                Thread.currentThread().getName());
    }

    /**
     * Checks if the current thread is not the main thread, otherwise throws.
     *
     * @throws IllegalStateException if current thread is the main thread.
     */
    public static void checkNotMainThread() {
        checkState(!Thread.currentThread().equals(Looper.getMainLooper().getThread()),
                "Method cannot be called on the main application thread (on: %s)",
                Thread.currentThread().getName());
    }

    private static String format(String template, Object... args) {
        template = String.valueOf(template); // null -> "null"

        // start substituting the arguments into the '%s' placeholders
        StringBuilder builder = new StringBuilder(
                template.length() + 16 * args.length);
        int templateStart = 0;
        int i = 0;
        while (i < args.length) {
            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();
    }
}