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/*
 * Copyright (C) 2013 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 java.util;

import java.util.function.Supplier;

/**
 * Utility methods for objects.
 *
 * @since 1.7
 */
public final class Objects {
	private Objects() {
	}

	/**
	 * Returns 0 if {@code a == b}, or {@code c.compare(a, b)} otherwise.
	 * That is, this makes {@code c} null-safe.
	 */
	public static  int compare(T a, T b, Comparator c) {
		return (a != b) ? c.compare(a, b) : 0;
	}

	/**
	 * Returns true if both arguments are null,
	 * the result of {@link Arrays#equals} if both arguments are primitive arrays,
	 * the result of {@link Arrays#deepEquals} if both arguments are arrays of reference types,
	 * and the result of {@link #equals} otherwise.
	 */
	public static boolean deepEquals(Object a, Object b) {
		if (a == null || b == null) {
			return a == b;
		} else if (a instanceof Object[] && b instanceof Object[]) {
			return Arrays.deepEquals((Object[]) a, (Object[]) b);
		} else if (a instanceof boolean[] && b instanceof boolean[]) {
			return Arrays.equals((boolean[]) a, (boolean[]) b);
		} else if (a instanceof byte[] && b instanceof byte[]) {
			return Arrays.equals((byte[]) a, (byte[]) b);
		} else if (a instanceof char[] && b instanceof char[]) {
			return Arrays.equals((char[]) a, (char[]) b);
		} else if (a instanceof double[] && b instanceof double[]) {
			return Arrays.equals((double[]) a, (double[]) b);
		} else if (a instanceof float[] && b instanceof float[]) {
			return Arrays.equals((float[]) a, (float[]) b);
		} else if (a instanceof int[] && b instanceof int[]) {
			return Arrays.equals((int[]) a, (int[]) b);
		} else if (a instanceof long[] && b instanceof long[]) {
			return Arrays.equals((long[]) a, (long[]) b);
		} else if (a instanceof short[] && b instanceof short[]) {
			return Arrays.equals((short[]) a, (short[]) b);
		}
		return a.equals(b);
	}

	/**
	 * Null-safe equivalent of {@code a.equals(b)}.
	 */
	public static boolean equals(Object a, Object b) {
		return (a == null) ? (b == null) : a.equals(b);
	}

	/**
	 * Convenience wrapper for {@link Arrays#hashCode}, adding varargs.
	 * This can be used to compute a hash code for an object's fields as follows:
	 * {@code Objects.hash(a, b, c)}.
	 */
	public static int hash(Object... values) {
		return Arrays.hashCode(values);
	}

	/**
	 * Returns 0 for null or {@code o.hashCode()}.
	 */
	public static int hashCode(Object o) {
		return (o == null) ? 0 : o.hashCode();
	}

	/**
	 * Returns {@code o} if non-null, or throws {@code NullPointerException}.
	 */
	public static  T requireNonNull(T o) {
		if (o == null) {
			throw new NullPointerException();
		}
		return o;
	}

	/**
	 * Returns {@code o} if non-null, or throws {@code NullPointerException}
	 * with the given detail message.
	 */
	public static  T requireNonNull(T o, String message) {
		if (o == null) {
			throw new NullPointerException(message);
		}
		return o;
	}

	/**
	 * Returns "null" for null or {@code o.toString()}.
	 */
	public static String toString(Object o) {
		return (o == null) ? "null" : o.toString();
	}

	/**
	 * Returns {@code nullString} for null or {@code o.toString()}.
	 */
	public static String toString(Object o, String nullString) {
		return (o == null) ? nullString : o.toString();
	}

	public static boolean isNull(Object obj) {
		return obj == null;
	}

	public static boolean nonNull(Object obj) {
		return obj != null;
	}

	public static  T requireNonNull(T obj, Supplier messageSupplier) {
		if (obj == null) throw new NullPointerException(messageSupplier.get());
		return obj;
	}
}