Convert a byte array into an int array in java

Question

Is there was a way to convert a hole array of bytes (lets say 1024) into an int array of total 256 integers without using something similar to this:

int result = 0;   
    result = b[0] & MASK;
    result = result + ((b[1] & MASK) << 8);
    result = result + ((b[2] & MASK) << 16);
    result = result + ((b[3] & MASK) << 24);            
return result;

Louis Wasserman · Accepted Answer · 2017-03-28 20:25:44Z

4

An int array? No, there isn't. You might be able to get other APIs that are similar to arrays, but even so they'll be doing something like that underneath. For example, ByteBuffer.wrap(array).asIntBuffer() would do that: it'd give you an array-like API, but underneath it'd be doing exactly what you say.

answered Mar 28, 2017 at 20:25

Louis Wasserman

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Peter Lawrey · Accepted Answer · 2017-03-28 21:22:26Z

1

You can use Unsafe but probably shouldn't

    try {
        Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
        theUnsafe.setAccessible(true);
        UNSAFE = (Unsafe) theUnsafe.get(null);
    } catch (Exception e) {
        throw new AssertionError(e);
    }


    byte[] bytes = new byte[128];
    for (int i = 0; i < bytes.length; i++) bytes[i] = (byte) i;
    int[] ints = new int[bytes.length / Integer.BYTES];
    UNSAFE.copyMemory(bytes, Unsafe.ARRAY_BYTE_BASE_OFFSET, ints, Unsafe.ARRAY_INT_BASE_OFFSET, bytes.length);
    for (int i : ints)
        System.out.printf("%08x%n", i);

answered Mar 28, 2017 at 21:22

Peter Lawrey

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