Java tutorial
/* * Copyright (C) 2009 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.google.common.primitives; import static com.google.common.base.Preconditions.checkArgument; import static com.google.common.base.Preconditions.checkNotNull; import com.google.common.annotations.GwtCompatible; import java.util.Comparator; import javax.annotation.CheckReturnValue; /** * Static utility methods pertaining to {@code byte} primitives that * interpret values as signed. The corresponding methods that treat the values * as unsigned are found in {@link UnsignedBytes}, and the methods for which * signedness is not an issue are in {@link Bytes}. * * <p>See the Guava User Guide article on <a href= * "https://github.com/google/guava/wiki/PrimitivesExplained"> * primitive utilities</a>. * * @author Kevin Bourrillion * @since 1.0 */ // TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT // javadoc? @CheckReturnValue @GwtCompatible public final class SignedBytes { private SignedBytes() { } /** * The largest power of two that can be represented as a signed {@code byte}. * * @since 10.0 */ public static final byte MAX_POWER_OF_TWO = 1 << 6; /** * Returns the {@code byte} value that is equal to {@code value}, if possible. * * @param value any value in the range of the {@code byte} type * @return the {@code byte} value that equals {@code value} * @throws IllegalArgumentException if {@code value} is greater than {@link * Byte#MAX_VALUE} or less than {@link Byte#MIN_VALUE} */ public static byte checkedCast(long value) { byte result = (byte) value; if (result != value) { // don't use checkArgument here, to avoid boxing throw new IllegalArgumentException("Out of range: " + value); } return result; } /** * Returns the {@code byte} nearest in value to {@code value}. * * @param value any {@code long} value * @return the same value cast to {@code byte} if it is in the range of the * {@code byte} type, {@link Byte#MAX_VALUE} if it is too large, * or {@link Byte#MIN_VALUE} if it is too small */ public static byte saturatedCast(long value) { if (value > Byte.MAX_VALUE) { return Byte.MAX_VALUE; } if (value < Byte.MIN_VALUE) { return Byte.MIN_VALUE; } return (byte) value; } /** * Compares the two specified {@code byte} values. The sign of the value * returned is the same as that of {@code ((Byte) a).compareTo(b)}. * * <p><b>Note:</b> this method behaves identically to the JDK 7 method {@link * Byte#compare}. * * @param a the first {@code byte} to compare * @param b the second {@code byte} to compare * @return a negative value if {@code a} is less than {@code b}; a positive * value if {@code a} is greater than {@code b}; or zero if they are equal */ // TODO(kevinb): if Ints.compare etc. are ever removed, *maybe* remove this // one too, which would leave compare methods only on the Unsigned* classes. public static int compare(byte a, byte b) { return a - b; // safe due to restricted range } /** * Returns the least value present in {@code array}. * * @param array a <i>nonempty</i> array of {@code byte} values * @return the value present in {@code array} that is less than or equal to * every other value in the array * @throws IllegalArgumentException if {@code array} is empty */ public static byte min(byte... array) { checkArgument(array.length > 0); byte min = array[0]; for (int i = 1; i < array.length; i++) { if (array[i] < min) { min = array[i]; } } return min; } /** * Returns the greatest value present in {@code array}. * * @param array a <i>nonempty</i> array of {@code byte} values * @return the value present in {@code array} that is greater than or equal to * every other value in the array * @throws IllegalArgumentException if {@code array} is empty */ public static byte max(byte... array) { checkArgument(array.length > 0); byte max = array[0]; for (int i = 1; i < array.length; i++) { if (array[i] > max) { max = array[i]; } } return max; } /** * Returns a string containing the supplied {@code byte} values separated * by {@code separator}. For example, {@code join(":", 0x01, 0x02, -0x01)} * returns the string {@code "1:2:-1"}. * * @param separator the text that should appear between consecutive values in * the resulting string (but not at the start or end) * @param array an array of {@code byte} values, possibly empty */ public static String join(String separator, byte... array) { checkNotNull(separator); if (array.length == 0) { return ""; } // For pre-sizing a builder, just get the right order of magnitude StringBuilder builder = new StringBuilder(array.length * 5); builder.append(array[0]); for (int i = 1; i < array.length; i++) { builder.append(separator).append(array[i]); } return builder.toString(); } /** * Returns a comparator that compares two {@code byte} arrays * lexicographically. That is, it compares, using {@link * #compare(byte, byte)}), the first pair of values that follow any common * prefix, or when one array is a prefix of the other, treats the shorter * array as the lesser. For example, {@code [] < [0x01] < [0x01, 0x80] < * [0x01, 0x7F] < [0x02]}. Values are treated as signed. * * <p>The returned comparator is inconsistent with {@link * Object#equals(Object)} (since arrays support only identity equality), but * it is consistent with {@link java.util.Arrays#equals(byte[], byte[])}. * * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order"> * Lexicographical order article at Wikipedia</a> * @since 2.0 */ public static Comparator<byte[]> lexicographicalComparator() { return LexicographicalComparator.INSTANCE; } private enum LexicographicalComparator implements Comparator<byte[]> { INSTANCE; @Override public int compare(byte[] left, byte[] right) { int minLength = Math.min(left.length, right.length); for (int i = 0; i < minLength; i++) { int result = SignedBytes.compare(left[i], right[i]); if (result != 0) { return result; } } return left.length - right.length; } } }