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HashCodeHelpers.javaAPI DocAndroid 5.1 API4237Thu Mar 12 22:22:10 GMT 2015android.hardware.camera2.utils

HashCodeHelpers

public final class HashCodeHelpers extends Object
Provide hashing functions using the Modified Bernstein hash

Fields Summary
Constructors Summary
Methods Summary
public static inthashCode(int[] array)
Hash every element uniformly using the Modified Bernstein hash.

Useful to implement a {@link Object#hashCode} for uniformly distributed data.

param
array a non-{@code null} array of integers
return
the numeric hash code

        if (array == null) {
            return 0;
        }

        /*
         *  Note that we use 31 here instead of 33 since it's preferred in Effective Java
         *  and used elsewhere in the runtime (e.g. Arrays#hashCode)
         *
         *  That being said 33 and 31 are nearly identical in terms of their usefulness
         *  according to http://svn.apache.org/repos/asf/apr/apr/trunk/tables/apr_hash.c
         */
        int h = 1;
        for (int x : array) {
            // Strength reduction; in case the compiler has illusions about divisions being faster
            h = ((h << 5) - h) ^ x; // (h * 31) XOR x
        }

        return h;
public static inthashCode(int x, int y, int z)

        return hashCode(new int[] { x, y, z } );
public static inthashCode(int x, int y, int z, int w)

        return hashCode(new int[] { x, y, z, w } );
public static inthashCode(int x, int y, int z, int w, int t)

        return hashCode(new int[] { x, y, z, w, t } );
public static inthashCode(float[] array)
Hash every element uniformly using the Modified Bernstein hash.

Useful to implement a {@link Object#hashCode} for uniformly distributed data.

param
array a non-{@code null} array of floats
return
the numeric hash code

        if (array == null) {
            return 0;
        }

        int h = 1;
        for (float f : array) {
            int x = Float.floatToIntBits(f);
            h = ((h << 5) - h) ^ x; // (h * 31) XOR x
        }

        return h;
public static inthashCode(T[] array)
Hash every element uniformly using the Modified Bernstein hash.

Useful to implement a {@link Object#hashCode} for uniformly distributed data.

param
array a non-{@code null} array of objects
return
the numeric hash code

        if (array == null) {
            return 0;
        }

        int h = 1;
        for (T o : array) {
            int x = (o == null) ? 0 : o.hashCode();
            h = ((h << 5) - h) ^ x; // (h * 31) XOR x
        }

        return h;
public static inthashCode(T a)

        return (a == null) ? 0 : a.hashCode();
public static inthashCode(T a, T b)

        int h = hashCode(a);

        int x = (b == null) ? 0 : b.hashCode();
        h = ((h << 5) - h) ^ x; // (h * 31) XOR x

        return h;
public static inthashCode(T a, T b, T c)

        int h = hashCode(a, b);

        int x = (c == null) ? 0 : c.hashCode();
        h = ((h << 5) - h) ^ x; // (h * 31) XOR x

        return h;
public static inthashCode(T a, T b, T c, T d)

        int h = hashCode(a, b, c);

        int x = (d == null) ? 0 : d.hashCode();
        h = ((h << 5) - h) ^ x; // (h * 31) XOR x

        return h;
public static inthashCode(int x)

        return hashCode(new int[] { x } );
public static inthashCode(int x, int y)

        return hashCode(new int[] { x, y } );