Java example source code file (HashCodeTest.java)

This example Java source code file (HashCodeTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

classsanitytester, expectedhashcode, hash_abcd, hashcode, hashcodetest, illegalargumentexception, illegalstateexception, immutablelist, indexoutofboundsexception, long, string, testcase, util

The HashCodeTest.java Java example source code

/*
 * Copyright (C) 2011 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.hash;

import static com.google.common.io.BaseEncoding.base16;

import com.google.common.base.Charsets;
import com.google.common.collect.ImmutableList;
import com.google.common.io.BaseEncoding;
import com.google.common.testing.ClassSanityTester;

import junit.framework.TestCase;

import java.util.Arrays;

/**
 * Unit tests for {@link HashCode}.
 *
 * @author Dimitris Andreou
 * @author Kurt Alfred Kluever
 */
public class HashCodeTest extends TestCase {
  // note: asInt(), asLong() are in little endian
  private static final ImmutableList<ExpectedHashCode> expectedHashCodes = ImmutableList.of(
      new ExpectedHashCode(new byte[] {
        (byte) 0xef, (byte) 0xcd, (byte) 0xab, (byte) 0x89,
        (byte) 0x67, (byte) 0x45, (byte) 0x23, (byte) 0x01},
        0x89abcdef, 0x0123456789abcdefL, "efcdab8967452301"),

      new ExpectedHashCode(new byte[] {
        (byte) 0xef, (byte) 0xcd, (byte) 0xab, (byte) 0x89,
        (byte) 0x67, (byte) 0x45, (byte) 0x23, (byte) 0x01, // up to here, same bytes as above
        (byte) 0x01, (byte) 0x02, (byte) 0x03, (byte) 0x04,
        (byte) 0x05, (byte) 0x06, (byte) 0x07, (byte) 0x08},
        0x89abcdef, 0x0123456789abcdefL, // asInt/asLong as above, due to equal eight first bytes
        "efcdab89674523010102030405060708"),

      new ExpectedHashCode(new byte[] { (byte) 0xdf, (byte) 0x9b, (byte) 0x57, (byte) 0x13 },
        0x13579bdf, null, "df9b5713"),

      new ExpectedHashCode(new byte[] {
          (byte) 0xcd, (byte) 0xab, (byte) 0x00, (byte) 0x00},
          0x0000abcd, null, "cdab0000"),

      new ExpectedHashCode(new byte[] {
          (byte) 0xef, (byte) 0xcd, (byte) 0xab, (byte) 0x00,
          (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00},
          0x00abcdef, 0x0000000000abcdefL, "efcdab0000000000")
    );

  // expectedHashCodes must contain at least one hash code with 4 bytes
  public void testFromInt() {
    for (ExpectedHashCode expected : expectedHashCodes) {
      if (expected.bytes.length == 4) {
        HashCode fromInt = HashCode.fromInt(expected.asInt);
        assertExpectedHashCode(expected, fromInt);
      }
    }
  }

  // expectedHashCodes must contain at least one hash code with 8 bytes
  public void testFromLong() {
    for (ExpectedHashCode expected : expectedHashCodes) {
      if (expected.bytes.length == 8) {
        HashCode fromLong = HashCode.fromLong(expected.asLong);
        assertExpectedHashCode(expected, fromLong);
      }
    }
  }

  public void testFromBytes() {
    for (ExpectedHashCode expected : expectedHashCodes) {
      HashCode fromBytes = HashCode.fromBytes(expected.bytes);
      assertExpectedHashCode(expected, fromBytes);
    }
  }

  public void testFromBytes_copyOccurs() {
    byte[] bytes = new byte[] { (byte) 0xcd, (byte) 0xab, (byte) 0x00, (byte) 0x00 };
    HashCode hashCode = HashCode.fromBytes(bytes);
    int expectedInt = 0x0000abcd;
    String expectedToString = "cdab0000";

    assertEquals(expectedInt, hashCode.asInt());
    assertEquals(expectedToString, hashCode.toString());

    bytes[0] = (byte) 0x00;

    assertEquals(expectedInt, hashCode.asInt());
    assertEquals(expectedToString, hashCode.toString());
  }

  public void testFromBytesNoCopy_noCopyOccurs() {
    byte[] bytes = new byte[] { (byte) 0xcd, (byte) 0xab, (byte) 0x00, (byte) 0x00 };
    HashCode hashCode = HashCode.fromBytesNoCopy(bytes);

    assertEquals(0x0000abcd, hashCode.asInt());
    assertEquals("cdab0000", hashCode.toString());

    bytes[0] = (byte) 0x00;

    assertEquals(0x0000ab00, hashCode.asInt());
    assertEquals("00ab0000", hashCode.toString());
  }

  public void testGetBytesInternal_noCloneOccurs() {
    byte[] bytes = new byte[] { (byte) 0xcd, (byte) 0xab, (byte) 0x00, (byte) 0x00 };
    HashCode hashCode = HashCode.fromBytes(bytes);

    assertEquals(0x0000abcd, hashCode.asInt());
    assertEquals("cdab0000", hashCode.toString());

    hashCode.getBytesInternal()[0] = (byte) 0x00;

    assertEquals(0x0000ab00, hashCode.asInt());
    assertEquals("00ab0000", hashCode.toString());
  }

  public void testPadToLong() {
    assertEquals(0x1111111111111111L, HashCode.fromLong(0x1111111111111111L).padToLong());
    assertEquals(0x9999999999999999L, HashCode.fromLong(0x9999999999999999L).padToLong());
    assertEquals(0x0000000011111111L, HashCode.fromInt(0x11111111).padToLong());
    assertEquals(0x0000000099999999L, HashCode.fromInt(0x99999999).padToLong());
  }

  public void testPadToLongWith4Bytes() {
    assertEquals(0x0000000099999999L, HashCode.fromBytesNoCopy(byteArrayWith9s(4)).padToLong());
  }

  public void testPadToLongWith6Bytes() {
    assertEquals(0x0000999999999999L, HashCode.fromBytesNoCopy(byteArrayWith9s(6)).padToLong());
  }

  public void testPadToLongWith8Bytes() {
    assertEquals(0x9999999999999999L, HashCode.fromBytesNoCopy(byteArrayWith9s(8)).padToLong());
  }

  private static byte[] byteArrayWith9s(int size) {
    byte[] bytez = new byte[size];
    Arrays.fill(bytez, (byte) 0x99);
    return bytez;
  }

  public void testToString() {
    byte[] data = new byte[] { 127, -128, 5, -1, 14 };
    assertEquals("7f8005ff0e", HashCode.fromBytes(data).toString());
    assertEquals("7f8005ff0e", base16().lowerCase().encode(data));
  }

  public void testHashCode_nulls() throws Exception {
    sanityTester().testNulls();
  }

  public void testHashCode_equalsAndSerializable() throws Exception {
    sanityTester().testEqualsAndSerializable();
  }

  public void testRoundTripHashCodeUsingBaseEncoding() {
    HashCode hash1 = Hashing.sha1().hashString("foo", Charsets.US_ASCII);
    HashCode hash2 =
        HashCode.fromBytes(BaseEncoding.base16().lowerCase().decode(hash1.toString()));
    assertEquals(hash1, hash2);
  }

  public void testObjectHashCode() {
    HashCode hashCode42 = HashCode.fromInt(42);
    assertEquals(42, hashCode42.hashCode());
  }

  // See https://code.google.com/p/guava-libraries/issues/detail?id=1494
  public void testObjectHashCodeWithSameLowOrderBytes() {
    // These will have the same first 4 bytes (all 0).
    byte[] bytesA = new byte[5];
    byte[] bytesB = new byte[5];

    // Change only the last (5th) byte
    bytesA[4] = (byte) 0xbe;
    bytesB[4] = (byte) 0xef;

    HashCode hashCodeA = HashCode.fromBytes(bytesA);
    HashCode hashCodeB = HashCode.fromBytes(bytesB);

    // They aren't equal...
    assertFalse(hashCodeA.equals(hashCodeB));

    // But they still have the same Object#hashCode() value.
    // Technically not a violation of the equals/hashCode contract, but...?
    assertEquals(hashCodeA.hashCode(), hashCodeB.hashCode());
  }

  public void testRoundTripHashCodeUsingFromString() {
    HashCode hash1 = Hashing.sha1().hashString("foo", Charsets.US_ASCII);
    HashCode hash2 = HashCode.fromString(hash1.toString());
    assertEquals(hash1, hash2);
  }

  public void testRoundTrip() {
    for (ExpectedHashCode expected : expectedHashCodes) {
      String string = HashCode.fromBytes(expected.bytes).toString();
      assertEquals(expected.toString, string);
      assertEquals(
          expected.toString,
          HashCode.fromBytes(
              BaseEncoding.base16().lowerCase().decode(string)).toString());
    }
  }

  public void testFromStringFailsWithInvalidHexChar() {
    try {
      HashCode.fromString("7f8005ff0z");
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testFromStringFailsWithUpperCaseString() {
    String string = Hashing.sha1().hashString("foo", Charsets.US_ASCII).toString().toUpperCase();
    try {
      HashCode.fromString(string);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testFromStringFailsWithShortInputs() {
    try {
      HashCode.fromString("");
      fail();
    } catch (IllegalArgumentException expected) {
    }
    try {
      HashCode.fromString("7");
      fail();
    } catch (IllegalArgumentException expected) {
    }
    HashCode unused = HashCode.fromString("7f");
  }

  public void testFromStringFailsWithOddLengthInput() {
    try {
      HashCode.fromString("7f8");
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testIntWriteBytesTo() {
    byte[] dest = new byte[4];
    HashCode.fromInt(42).writeBytesTo(dest, 0, 4);
    assertTrue(Arrays.equals(
        HashCode.fromInt(42).asBytes(),
        dest));
  }

  public void testLongWriteBytesTo() {
    byte[] dest = new byte[8];
    HashCode.fromLong(42).writeBytesTo(dest, 0, 8);
    assertTrue(Arrays.equals(
        HashCode.fromLong(42).asBytes(),
        dest));
  }

  private static final HashCode HASH_ABCD =
      HashCode.fromBytes(new byte[] { (byte) 0xaa, (byte) 0xbb, (byte) 0xcc, (byte) 0xdd });

  public void testWriteBytesTo() {
    byte[] dest = new byte[4];
    HASH_ABCD.writeBytesTo(dest, 0, 4);
    assertTrue(Arrays.equals(
        new byte[] { (byte) 0xaa, (byte) 0xbb, (byte) 0xcc, (byte) 0xdd },
        dest));
  }

  public void testWriteBytesToOversizedArray() {
    byte[] dest = new byte[5];
    HASH_ABCD.writeBytesTo(dest, 0, 4);
    assertTrue(Arrays.equals(
        new byte[] { (byte) 0xaa, (byte) 0xbb, (byte) 0xcc, (byte) 0xdd, (byte) 0x00 },
        dest));
  }

  public void testWriteBytesToOversizedArrayLongMaxLength() {
    byte[] dest = new byte[5];
    HASH_ABCD.writeBytesTo(dest, 0, 5);
    assertTrue(Arrays.equals(
        new byte[] { (byte) 0xaa, (byte) 0xbb, (byte) 0xcc, (byte) 0xdd, (byte) 0x00 },
        dest));
  }

  public void testWriteBytesToOversizedArrayShortMaxLength() {
    byte[] dest = new byte[5];
    HASH_ABCD.writeBytesTo(dest, 0, 3);
    assertTrue(Arrays.equals(
        new byte[] { (byte) 0xaa, (byte) 0xbb, (byte) 0xcc, (byte) 0x00, (byte) 0x00 },
        dest));
  }

  public void testWriteBytesToUndersizedArray() {
    byte[] dest = new byte[3];
    try {
      HASH_ABCD.writeBytesTo(dest, 0, 4);
      fail();
    } catch (IndexOutOfBoundsException expected) {
    }
  }

  public void testWriteBytesToUndersizedArrayLongMaxLength() {
    byte[] dest = new byte[3];
    try {
      HASH_ABCD.writeBytesTo(dest, 0, 5);
      fail();
    } catch (IndexOutOfBoundsException expected) {
    }
  }

  public void testWriteBytesToUndersizedArrayShortMaxLength() {
    byte[] dest = new byte[3];
    HASH_ABCD.writeBytesTo(dest, 0, 2);
    assertTrue(Arrays.equals(
        new byte[] { (byte) 0xaa, (byte) 0xbb, (byte) 0x00 },
        dest));
  }

  private static ClassSanityTester.FactoryMethodReturnValueTester sanityTester() {
    return new ClassSanityTester()
        .setDefault(byte[].class, new byte[] {1, 2, 3, 4})
        .setDistinctValues(byte[].class, new byte[] {1, 2, 3, 4}, new byte[] {5, 6, 7, 8})
        .setDistinctValues(String.class, "7f8005ff0e", "7f8005ff0f")
        .forAllPublicStaticMethods(HashCode.class);
  }

  private static void assertExpectedHashCode(ExpectedHashCode expectedHashCode, HashCode hash) {
    assertTrue(Arrays.equals(expectedHashCode.bytes, hash.asBytes()));
    byte[] bb = new byte[hash.bits() / 8];
    hash.writeBytesTo(bb, 0, bb.length);
    assertTrue(Arrays.equals(expectedHashCode.bytes, bb));
    assertEquals(expectedHashCode.asInt, hash.asInt());
    if (expectedHashCode.asLong == null) {
      try {
        hash.asLong();
        fail();
      } catch (IllegalStateException expected) {}
    } else {
      assertEquals(expectedHashCode.asLong.longValue(), hash.asLong());
    }
    assertEquals(expectedHashCode.toString, hash.toString());
    assertSideEffectFree(hash);
    assertReadableBytes(hash);
  }

  private static void assertSideEffectFree(HashCode hash) {
    byte[] original = hash.asBytes();
    byte[] mutated = hash.asBytes();
    mutated[0]++;
    assertTrue(Arrays.equals(original, hash.asBytes()));
  }

  private static void assertReadableBytes(HashCode hashCode) {
    assertTrue(hashCode.bits() >= 32); // sanity
    byte[] hashBytes = hashCode.asBytes();
    int totalBytes = hashCode.bits() / 8;

    for (int bytes = 0; bytes < totalBytes; bytes++) {
      byte[] bb = new byte[bytes];
      hashCode.writeBytesTo(bb, 0, bb.length);

      assertTrue(Arrays.equals(Arrays.copyOf(hashBytes, bytes), bb));
    }
  }

  private static class ExpectedHashCode {
    final byte[] bytes;
    final int asInt;
    final Long asLong; // null means that asLong should throw an exception
    final String toString;
    ExpectedHashCode(byte[] bytes, int asInt, Long asLong, String toString) {
      this.bytes = bytes;
      this.asInt = asInt;
      this.asLong = asLong;
      this.toString = toString;
    }
  }
}