Java Tutorial/Class Definition/hashCode
Содержание
- 1 A very efficient java hash algorithm, based on the BuzHash algoritm
- 2 Comparing Object Values Using Hash Codes
- 3 Computing hash codes
- 4 Get hash code for primitive data types
- 5 Get the identity hash codes
- 6 Implement hashCode using commons-lang
- 7 Null Safe Hash Code
- 8 Returns an integer hash code representing the given double array value.
- 9 Secure Hash
A very efficient java hash algorithm, based on the BuzHash algoritm
<source lang="java">
/*
* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */
/**
* A very efficient java hash algorithm, based on the BuzHash algoritm by Robert * Uzgalis (see http://www.serve.net/buz/hash.adt/java.000.html for more * information). BuzHash is Copyright (c)1996 Robert Uzgalis, All Rights * Reserved. Used with kind permission of the author * * @version $Id: HashUtil.java 587751 2007-10-24 02:41:36Z vgritsenko $ */
public final class HashUtil {
private static long initial_hash = 0xe12398c6d9ae3b8aL; // initial values private static long mix_master[/* 0:255 */] = { /* 000 */0x4476081a7043a46fL, 0x45768b8a6e7eac19L, 0xebd556c1cf055952L, /* */0x72ed2da1bf010101L, 0x3ff2030b128e8a64L, /* 005 */0xcbc330238adcfef2L, 0x737807fe42e20c6cL, 0x74dabaedb1095c58L, /* */0x968f065c65361d67L, 0xd3f4018ac7a4b199L, /* 010 */0x954b389b52f24df2L, 0x2f97a9d8d0549327L, 0xb9bea2b49a3b180fL, /* */0xaf2f42536b21f2ebL, 0x85d991663cff1325L, /* 015 */0xb9e1260207b575b9L, 0xf3ea88398a23b7e2L, 0xfaf8c83ffbd9091dL, /* */0x4274fe90834dbdf9L, 0x3f20b157b68d6313L, /* 020 */0x68b48972b6d06b93L, 0x694837b6eba548afL, 0xeecb51d1acc917c9L, /* */0xf1c633f02dffbcfaL, 0xa6549ec9d301f3b5L, /* 025 */0x451dc944f1663592L, 0x446d6acef6ce9e4fL, 0x1c8a5b3013206f02L, /* */0x5908ca36f2dc50f7L, 0x4fd55d3f3e880a87L, /* 030 */0xa03a8dbeabbf065dL, 0x3ccbbe078fabcb6dL, 0x1da53a259116f2d0L, /* */0xfb27a96fcb9af152L, 0x50aba242e85aec09L, /* 035 */0x24d4e414fc4fc987L, 0x83971844a9ce535eL, 0xc26a3fdeb849398eL, /* */0xc2380d044d2e70d8L, 0xab418aa8ae19b18fL, /* 040 */0xd95b6b9247d5ebeaL, 0x8b3b2171fdc60511L, 0xe15cd0ae3fcc44afL, /* */0x5a4e27f914a68f17L, 0x377bd28ca09aafdcL, /* 045 */0xbbeb9828594a3294L, 0x7c8df263ae1de1b9L, 0xba0a48a5fd1c1dd0L, /* */0x57cc1b8818b98ee6L, 0x8c570975d357dabcL, /* 050 */0x76bdcd6f2e8826aaL, 0x529b15b6ec4055f1L, 0x9147c7a54c34f8a9L, /* */0x2f96a7728170e402L, 0xe46602f455eca72eL, /* 055 */0x22834c4dd1bde03fL, 0x2644cf5a25e368ffL, 0x907c6de90b120f4aL, /* */0xadfe8ba99028f728L, 0xa85199ae14df0433L, /* 060 */0x2d749b946dd3601eL, 0x76e35457aa052772L, 0x90410bf6e427f736L, /* */0x536ad04d13e35041L, 0x8cc0d76769b76914L, /* 065 */0xae0249f6e3b3c01cL, 0x1bdfd075307d6fafL, 0xd8e04f70c221deccL, /* */0x4ab23622a4281a5dL, 0x37a5613da2fcaba7L, /* 070 */0x19a56203666d4a9fL, 0x158ffab502c4be93L, 0x0bee714e332ecb2fL, /* */0x69b71a59f6f74ab0L, 0x0fc7fc622f1dfe8fL, /* 075 */0x513966de7152a6f9L, 0xc16fae9cc2ea9be7L, 0xb66f0ac586c1899eL, /* */0x11e124aee3bdefd7L, 0x86cf5a577512901bL, /* 080 */0x33f33ba6994a1fbdL, 0xde6c4d1d3d47ff0dL, 0x6a99220dc6f78e66L, /* */0x2dc06ca93e2d25d2L, 0x96413b520134d573L, /* 085 */0xb4715ce8e1023afaL, 0xe6a75900c8c66c0aL, 0x6448f13ad54c12edL, /* */0xb9057c28cf6689f0L, 0xf4023daf67f7677aL, /* 090 */0x877c2650767b9867L, 0xb7ea587dcd5b2341L, 0xc048cf111733f9bcL, /* */0x112012c15bc867bfL, 0xc95f52b1d9418811L, /* 095 */0xa47e624ee7499083L, 0x26928606df9b12e8L, 0x5d020462ec3e0928L, /* */0x8bbde651f6d08914L, 0xd5db83db758e524aL, /* 100 */0x3105e355c000f455L, 0xdd7fe1b81a786c79L, 0x1f3a818c8e012db1L, /* */0xd902de819d7b42faL, 0x4200e63325cda5f0L, /* 105 */0x0e919cdc5fba9220L, 0x5360dd54605a11e1L, 0xa3182d0e6cb23e6cL, /* */0x13ee462c1b483b87L, 0x1b1b6087b997ee22L, /* 110 */0x81c36d0b877f7362L, 0xc24879932c1768d4L, 0x1faa756e1673f9adL, /* */0x61651b24d11fe93dL, 0x30fe3d9304e1cde4L, /* 115 */0x7be867c750747250L, 0x973e52c7005b5db6L, 0x75d6b699bbaf4817L, /* */0x25d2a9e97379e196L, 0xe65fb599aca98701L, /* 120 */0x6ac27960d24bde84L, 0xdfacc04c9fabbcb6L, 0xa46cd07f4a97882bL, /* */0x652031d8e59a1fd8L, 0x1185bd967ec7ce10L, /* 125 */0xfc9bd84c6780f244L, 0x0a0c59872f61b3ffL, 0x63885727a1c71c95L, /* */0x5e88b4390b2d765cL, 0xf0005ccaf988514dL, /* 130 */0x474e44280a98e840L, 0x32de151c1411bc42L, 0x2c4b86d5aa4482c2L, /* */0xccd93deb2d9d47daL, 0x3743236ff128a622L, /* 135 */0x42ed2f2635ba5647L, 0x99c74afd18962dbdL, 0x2d663bb870f6d242L, /* */0x7912033bc7635d81L, 0xb442862f43753680L, /* 140 */0x94b1a5400aeaab4cL, 0x5ce285fe810f2220L, 0xe8a7dbe565d9c0b1L, /* */0x219131af78356c94L, 0x7b3a80d130f27e2fL, /* 145 */0xbaa5d2859d16b440L, 0x821cfb6935771070L, 0xf68cfb6ee9bc2336L, /* */0x18244132e935d2fdL, 0x2ed0bda1f4720cffL, /* 150 */0x4ed48cdf6975173cL, 0xfd37a7a2520e2405L, 0x82c102b2a9e73ce2L, /* */0xadac6517062623a7L, 0x5a1294d318e26104L, /* 155 */0xea84fe65c0e4f061L, 0x4f96f8a9464cfee9L, 0x9831dff8ccdc534aL, /* */0x4ca927cd0f192a14L, 0x030900b294b71649L, /* 160 */0x644b263b9aeb0675L, 0xa601d4e34647e040L, 0x34d897eb397f1004L, /* */0xa6101c37f4ec8dfcL, 0xc29d2a8bbfd0006bL, /* 165 */0xc6b07df8c5b4ed0fL, 0xce1b7d92ba6bccbeL, 0xfa2f99442e03fe1bL, /* */0xd8863e4c16f0b363L, 0x033b2cccc3392942L, /* 170 */0x757dc33522d6cf9cL, 0xf07b1ff6ce55fec5L, 0x1569e75f09b40463L, /* */0xfa33fa08f14a310bL, 0x6eb79aa27bbcf76bL, /* 175 */0x157061207c249602L, 0x25e5a71fc4e99555L, 0x5df1fe93de625355L, /* */0x235b56090c1aa55dL, 0xe51068613eaced91L, /* 180 */0x45bd47b893b9ff1eL, 0x6595e1798d381f2dL, 0xc9b5848cbcdb5ba8L, /* */0x65985146ff7792bcL, 0x4ab4a17bf05a19a0L, /* 185 */0xfd94f4ca560ffb0cL, 0xcf9bad581a68fa68L, 0x92b4f0b502b1ce1aL, /* */0xbcbec0769a610474L, 0x8dbd31ded1a0fecbL, /* 190 */0xdd1f5ed9f90e8533L, 0x61c1e6a523f84d95L, 0xf24475f383c110c4L, /* */0xdb2dffa66f90588dL, 0xac06d88e9ee04455L, /* 195 */0xa215fc47c40504baL, 0x86d7caebfee93369L, 0x9eaec31985804099L, /* */0x0fba2214abe5d01bL, 0x5a32975a4b3865d6L, /* 200 */0x8cceebc98a5c108fL, 0x7e12c4589654f2dcL, 0xa49ad49fb0d19772L, /* */0x3d142dd9c406152bL, 0x9f13589e7be2b8a5L, /* 205 */0x5e8dbac1892967adL, 0xcc23b93a6308e597L, 0x1ef35f5fe874e16aL, /* */0x63ae9cc08d2e274fL, 0x5bbabee56007fc05L, /* 210 */0xabfd72994230fc39L, 0x9d71a13a99144de1L, 0xd9daf5aa8dcc89b3L, /* */0xe145ec0514161bfdL, 0x143befc2498cd270L, /* 215 */0xa8e192557dbbd9f8L, 0xcbeda2445628d7d0L, 0x997f0a93205d9ea4L, /* */0x01014a97f214ebfaL, 0x70c026ffd1ebedafL, /* 220 */0xf8737b1b3237002fL, 0x8afcbef3147e6e5eL, 0x0e1bb0684483ebd3L, /* */0x4cbad70ae9b05aa6L, 0xd4a31f523517c363L, /* 225 */0xdb0f057ae8e9e8a2L, 0x400894a919d89df6L, 0x6a626a9b62defab3L, /* */0xf907fd7e14f4e201L, 0xe10e4a5657c48f3fL, /* 230 */0xb17f9f54b8e6e5dcL, 0x6b9e69045fa6d27aL, 0x8b74b6a41dc3078eL, /* */0x027954d45ca367f9L, 0xd07207b8fdcbb7ccL, /* 235 */0xf397c47d2f36414bL, 0x05e4e8b11d3a034fL, 0x36adb3f7122d654fL, /* */0x607d9540eb336078L, 0xb639118e3a8b9600L, /* 240 */0xd0a406770b5f1484L, 0x3cbee8213ccfb7c6L, 0x467967bb2ff89cf1L, /* */0xb115fe29609919a6L, 0xba740e6ffa83287eL, /* 245 */0xb4e51be9b694b7cdL, 0xc9a081c677df5aeaL, 0x2e1fbcd8944508ccL, /* */0xf626e7895581fbb8L, 0x3ce6e9b5728a05cbL, /* 250 */0x46e87f2664a31712L, 0x8c1dc526c2f6acfaL, 0x7b4826726e560b10L, /* */0x2966e0099d8d7ce1L, 0xbb0dd5240d2b2adeL, 0x0d527cc60bbaa936L }; /** * This is buzhash the hash function on which most other Hash methods are * built. */ private static long buzhash(StringBuffer arg) { /* Hash StringBuffer */ long h = initial_hash; for (int i = 0; i < arg.length(); ++i) h = (h << 1) ^ (h >>> 63) ^ mix_master[(arg.charAt(i) ^ (arg.charAt(i) >>> 8)) & 0xff]; return h; } /** * This is buzhash the hash function on which most other Hash methods are * built. */ private static long buzhash(String arg) { /* Hash StringBuffer */ long h = initial_hash; for (int i = 0; i < arg.length(); ++i) h = (h << 1) ^ (h >>> 63) ^ mix_master[(arg.charAt(i) ^ (arg.charAt(i) >>> 8)) & 0xff]; return h; } /** * Hash a String. * * @param arg * The String to be hashed * @return The hash for the input. */ public static long hash(String arg) { // Make Hash from String return buzhash(arg); } /** * Hash a String. * * @param arg * The String represented by the StringBuffer to be hashed * @return The hash for the input. */ public static long hash(StringBuffer arg) { // Make Hash from StringBuffer return buzhash(arg); }
}</source>
Comparing Object Values Using Hash Codes
<source lang="java">
import java.io.File; public class Main {
public static void main(String[] argv) throws Exception { File file1 = new File("a"); File file2 = new File("a"); File file3 = new File("b"); int hc1 = file1.hashCode(); System.out.println(hc1); int hc2 = file2.hashCode(); System.out.println(hc2); int hc3 = file3.hashCode(); System.out.println(hc3); }
}</source>
Computing hash codes
<source lang="java">
/*
* JBoss DNA (http://www.jboss.org/dna) * See the COPYRIGHT.txt file distributed with this work for information * regarding copyright ownership. Some portions may be licensed * to Red Hat, Inc. under one or more contributor license agreements. * See the AUTHORS.txt file in the distribution for a full listing of * individual contributors. * * JBoss DNA is free software. Unless otherwise indicated, all code in JBoss DNA * is licensed to you under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * JBoss DNA is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this software; if not, write to the Free * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA * 02110-1301 USA, or see the FSF site: http://www.fsf.org. */
import java.util.Arrays; /**
* Utilities for easily computing hash codes. The algorithm should generally produce good distributions for use in hash-based * containers or collections, but as expected does always result in repeatable hash codes given the inputs. * @author Randall Hauch */
public class HashCode {
// Prime number used in improving distribution: 1,000,003 private static final int PRIME = 103; /** * Compute a combined hash code from the supplied objects. This method always returns 0 if no objects are supplied. * @param objects the objects that should be used to compute the hash code * @return the hash code */ public static int compute( Object... objects ) { return compute(0, objects); } /** * Compute a combined hash code from the supplied objects using the supplied seed. * @param seed a value upon which the hash code will be based; may be 0 * @param objects the objects that should be used to compute the hash code * @return the hash code */ protected static int compute( int seed, Object... objects ) { if (objects == null || objects.length == 0) { return seed * HashCode.PRIME; } // Compute the hash code for all of the objects ... int hc = seed; for (Object object : objects) { hc = HashCode.PRIME * hc; if (object instanceof byte[]) { hc += Arrays.hashCode((byte[])object); } else if (object instanceof boolean[]) { hc += Arrays.hashCode((boolean[])object); } else if (object instanceof short[]) { hc += Arrays.hashCode((short[])object); } else if (object instanceof int[]) { hc += Arrays.hashCode((int[])object); } else if (object instanceof long[]) { hc += Arrays.hashCode((long[])object); } else if (object instanceof float[]) { hc += Arrays.hashCode((float[])object); } else if (object instanceof double[]) { hc += Arrays.hashCode((double[])object); } else if (object instanceof char[]) { hc += Arrays.hashCode((char[])object); } else if (object instanceof Object[]) { hc += Arrays.hashCode((Object[])object); } else if (object != null) { hc += object.hashCode(); } } return hc; }
}</source>
Get hash code for primitive data types
<source lang="java">
import java.lang.reflect.Array; import java.util.Arrays; /*
* Copyright 2002-2007 the original author or 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. */
//Revised from springframework /**
* Miscellaneous object utility methods. Mainly for internal use within the * framework; consider Jakarta"s Commons Lang for a more comprehensive suite * of object utilities. * * @author Juergen Hoeller * @author Keith Donald * @author Rod Johnson * @author Rob Harrop * @author Alex Ruiz * @since 19.03.2004 * @see org.apache.rumons.lang.ObjectUtils */
abstract class ObjectUtils {
private static final int INITIAL_HASH = 7; private static final int MULTIPLIER = 31; private static final String EMPTY_STRING = ""; private static final String NULL_STRING = "null"; private static final String ARRAY_START = "{"; private static final String ARRAY_END = "}"; private static final String EMPTY_ARRAY = ARRAY_START + ARRAY_END; private static final String ARRAY_ELEMENT_SEPARATOR = ", ";
/** * Return the same value as{@link Boolean#hashCode()}
. * @see Boolean#hashCode() */ public static int hashCode(boolean bool) { return bool ? 1231 : 1237; } /** * Return the same value as{@link Double#hashCode()}
. * @see Double#hashCode() */ public static int hashCode(double dbl) { long bits = Double.doubleToLongBits(dbl); return hashCode(bits); } /** * Return the same value as{@link Float#hashCode()}
. * @see Float#hashCode() */ public static int hashCode(float flt) { return Float.floatToIntBits(flt); } /** * Return the same value as{@link Long#hashCode()}
. * @see Long#hashCode() */ public static int hashCode(long lng) { return (int) (lng ^ (lng >>> 32)); }
}</source>
Get the identity hash codes
<source lang="java">
import java.io.File; public class Main {
public static void main(String[] argv) throws Exception { File file1 = new File("a"); File file2 = new File("a"); File file3 = new File("b"); int ihc1 = System.identityHashCode(file1); System.out.println(ihc1); int ihc2 = System.identityHashCode(file2); System.out.println(ihc2); int ihc3 = System.identityHashCode(file3); System.out.println(ihc3); }
}</source>
Implement hashCode using commons-lang
<source lang="java">
import org.apache.rumons.lang.builder.HashCodeBuilder; import org.apache.rumons.lang.builder.EqualsBuilder; import java.io.Serializable; public class Main implements Serializable {
private Long id; private String title; private String author; public int hashCode() { return new HashCodeBuilder().append(id).append(title).append(author).toHashCode(); // return HashCodeBuilder.reflectionHashCode(this); }
}</source>
Null Safe Hash Code
<source lang="java">
import java.lang.reflect.Array; import java.util.Arrays; /*
* Copyright 2002-2007 the original author or 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. */
//Revised from springframework /**
* Miscellaneous object utility methods. Mainly for internal use within the * framework; consider Jakarta"s Commons Lang for a more comprehensive suite * of object utilities. * * @author Juergen Hoeller * @author Keith Donald * @author Rod Johnson * @author Rob Harrop * @author Alex Ruiz * @since 19.03.2004 * @see org.apache.rumons.lang.ObjectUtils */
abstract class ObjectUtils {
private static final int INITIAL_HASH = 7; private static final int MULTIPLIER = 31; private static final String EMPTY_STRING = ""; private static final String NULL_STRING = "null"; private static final String ARRAY_START = "{"; private static final String ARRAY_END = "}"; private static final String EMPTY_ARRAY = ARRAY_START + ARRAY_END; private static final String ARRAY_ELEMENT_SEPARATOR = ", ";
/** * Return a hash code based on the contents of the specified array. * Ifarray
isnull
, this method returns 0. */ public static int nullSafeHashCode(boolean[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + hashCode(array[i]); } return hash; } /** * Return a hash code based on the contents of the specified array. * Ifarray
isnull
, this method returns 0. */ public static int nullSafeHashCode(byte[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + array[i]; } return hash; } /** * Return a hash code based on the contents of the specified array. * Ifarray
isnull
, this method returns 0. */ public static int nullSafeHashCode(char[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + array[i]; } return hash; } /** * Return a hash code based on the contents of the specified array. * Ifarray
isnull
, this method returns 0. */ public static int nullSafeHashCode(double[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + hashCode(array[i]); } return hash; } /** * Return a hash code based on the contents of the specified array. * Ifarray
isnull
, this method returns 0. */ public static int nullSafeHashCode(float[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + hashCode(array[i]); } return hash; } /** * Return a hash code based on the contents of the specified array. * Ifarray
isnull
, this method returns 0. */ public static int nullSafeHashCode(int[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + array[i]; } return hash; } /** * Return a hash code based on the contents of the specified array. * Ifarray
isnull
, this method returns 0. */ public static int nullSafeHashCode(long[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + hashCode(array[i]); } return hash; } /** * Return a hash code based on the contents of the specified array. * Ifarray
isnull
, this method returns 0. */ public static int nullSafeHashCode(short[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + array[i]; } return hash; } /** * Return the same value as{@link Boolean#hashCode()}
. * @see Boolean#hashCode() */ public static int hashCode(boolean bool) { return bool ? 1231 : 1237; } /** * Return the same value as{@link Double#hashCode()}
. * @see Double#hashCode() */ public static int hashCode(double dbl) { long bits = Double.doubleToLongBits(dbl); return hashCode(bits); } /** * Return the same value as{@link Float#hashCode()}
. * @see Float#hashCode() */ public static int hashCode(float flt) { return Float.floatToIntBits(flt); } /** * Return the same value as{@link Long#hashCode()}
. * @see Long#hashCode() */ public static int hashCode(long lng) { return (int) (lng ^ (lng >>> 32)); }
}</source>
Returns an integer hash code representing the given double array value.
<source lang="java">
import java.io.File; /*
* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. * * */
public class Main {
/** * Returns an integer hash code representing the given double array value. * * @param value the value to be hashed (may be null) * @return the hash code * @since 1.2 */ public static int hash(double[] value) { if (value == null) { return 0; } int result = value.length; for (int i = 0; i < value.length; ++i) { result = result * 31 + hash(value[i]); } return result; } /** * Returns an integer hash code representing the given double value. * * @param value the value to be hashed * @return the hash code */ public static int hash(double value) { long bits = Double.doubleToLongBits(value); return (int)(bits ^ (bits >>> 32)); }
}</source>
Secure Hash
<source lang="java">
/*
* JBoss DNA (http://www.jboss.org/dna) * See the COPYRIGHT.txt file distributed with this work for information * regarding copyright ownership. Some portions may be licensed * to Red Hat, Inc. under one or more contributor license agreements. * See the AUTHORS.txt file in the distribution for a full listing of * individual contributors. * * JBoss DNA is free software. Unless otherwise indicated, all code in JBoss DNA * is licensed to you under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * JBoss DNA is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this software; if not, write to the Free * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA * 02110-1301 USA, or see the FSF site: http://www.fsf.org. */
import java.io.BufferedInputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; /**
* @author Randall Hauch */
public class SecureHash {
/** * Commonly-used hashing algorithms. */ public enum Algorithm { MD2("MD2", "The MD2 message digest algorithm as defined in RFC 1319"), MD5("MD5", "The MD5 message digest algorithm as defined in RFC 1321"), SHA_1("SHA-1", "The Secure Hash Algorithm, as defined in Secure Hash Standard, NIST FIPS 180-1"), SHA_256( "SHA-256", "New hash algorithms for which the draft Federal Information Processing Standard 180-2, " + "Secure Hash Standard (SHS) is now available. SHA-256 is a 256-bit hash function intended to provide 128 bits of " + "security against collision attacks."), SHA_384( "SHA-384", "New hash algorithms for which the draft Federal Information Processing Standard 180-2, " + "Secure Hash Standard (SHS) is now available. A 384-bit hash may be obtained by truncating the SHA-512 output."), SHA_512( "SHA-512", "New hash algorithms for which the draft Federal Information Processing Standard 180-2, " + "Secure Hash Standard (SHS) is now available. SHA-512 is a 512-bit hash function intended to provide 256 bits of security."); private String name; private String description; private Algorithm( String name, String description ) { this.name = name; this.description = description; } public String digestName() { return this.name; } public String description() { return this.description; } @Override public String toString() { return digestName(); } } /** * Get the hash of the supplied content, using the supplied digest algorithm. * * @param algorithm the hashing function algorithm that should be used * @param content the content to be hashed; may not be null * @return the hash of the contents as a byte array * @throws NoSuchAlgorithmException if the supplied algorithm could not be found * @throws IllegalArgumentException if the algorithm is null */ public static byte[] getHash( Algorithm algorithm, byte[] content ) throws NoSuchAlgorithmException { return getHash(algorithm.digestName(), content); } /** * Get the hash of the supplied content, using the supplied digest algorithm. * * @param algorithm the hashing function algorithm that should be used * @param file the file containing the content to be hashed; may not be null * @return the hash of the contents as a byte array * @throws NoSuchAlgorithmException if the supplied algorithm could not be found * @throws IllegalArgumentException if the algorithm is null * @throws IOException if there is an error reading the file */ public static byte[] getHash( Algorithm algorithm, File file ) throws NoSuchAlgorithmException, IOException { return getHash(algorithm.digestName(), file); } /** * Get the hash of the supplied content, using the supplied digest algorithm. * * @param algorithm the hashing function algorithm that should be used * @param stream the stream containing the content to be hashed; may not be null * @return the hash of the contents as a byte array * @throws NoSuchAlgorithmException if the supplied algorithm could not be found * @throws IllegalArgumentException if the algorithm is null * @throws IOException if there is an error reading the stream */ public static byte[] getHash( Algorithm algorithm, InputStream stream ) throws NoSuchAlgorithmException, IOException { return getHash(algorithm.digestName(), stream); } /** * Get the hash of the supplied content, using the digest identified by the supplied name. * * @param digestName the name of the hashing function (or {@link MessageDigest message digest}) that should be used * @param content the content to be hashed; may not be null * @return the hash of the contents as a byte array * @throws NoSuchAlgorithmException if the supplied algorithm could not be found */ public static byte[] getHash( String digestName, byte[] content ) throws NoSuchAlgorithmException { MessageDigest digest = MessageDigest.getInstance(digestName); assert digest != null; return digest.digest(content); } /** * Get the hash of the supplied content, using the digest identified by the supplied name. * * @param digestName the name of the hashing function (or {@link MessageDigest message digest}) that should be used * @param file the file whose content is to be hashed; may not be null * @return the hash of the contents as a byte array * @throws NoSuchAlgorithmException if the supplied algorithm could not be found * @throws IOException if there is an error reading the file */ public static byte[] getHash( String digestName, File file ) throws NoSuchAlgorithmException, IOException { MessageDigest digest = MessageDigest.getInstance(digestName); assert digest != null; InputStream in = new BufferedInputStream(new FileInputStream(file)); boolean error = false; try { int bufSize = 1024; byte[] buffer = new byte[bufSize]; int n = in.read(buffer, 0, bufSize); int count = 0; while (n != -1) { count += n; digest.update(buffer, 0, n); n = in.read(buffer, 0, bufSize); } } catch (IOException e) { error = true; throw e; } finally { try { in.close(); } catch (IOException e) { if (!error) throw e; } } return digest.digest(); } /** * Get the hash of the supplied content, using the digest identified by the supplied name. Note that this method never closes * the supplied stream. * * @param digestName the name of the hashing function (or {@link MessageDigest message digest}) that should be used * @param stream the stream containing the content to be hashed; may not be null * @return the hash of the contents as a byte array * @throws NoSuchAlgorithmException if the supplied algorithm could not be found * @throws IOException if there is an error reading the stream */ public static byte[] getHash( String digestName, InputStream stream ) throws NoSuchAlgorithmException, IOException { MessageDigest digest = MessageDigest.getInstance(digestName); assert digest != null; int bufSize = 1024; byte[] buffer = new byte[bufSize]; int n = stream.read(buffer, 0, bufSize); int count = 0; while (n != -1) { count += n; digest.update(buffer, 0, n); n = stream.read(buffer, 0, bufSize); } return digest.digest(); }
}</source>