Java Utililty Methods Bit Count

List of utility methods to do Bit Count

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Description

The list of methods to do Bit Count are organized into topic(s).

Method

intcountBits(int x)
count Bits 
x = (x & 0x55555555) + ((x >> 1) & 0x55555555);
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x & 0x0f0f0f0f) + ((x >> 4) & 0x0f0f0f0f);
x = (x & 0x00ff00ff) + ((x >> 8) & 0x00ff00ff);
x = (x & 0x0000ffff) + ((x >> 16) & 0x0000ffff);
return x;
bytecountBits(long num)
count 1 bits in nubmer. 
byte result;
for (result = 0; Math.abs(num) > 0; result++) {
    num &= num - 1;
return result;
intcountBits(long value)
count Bits 
int count = 0;
while (value > 0) {
    value >>= 1;
    count++;
return count;
intcountBitsInMask(int mask)
count Bits In Mask 
switch (mask) {
case -1:
    return 32;
case 0:
    return 0;
case 1:
case 2:
case 4:
...
intcountBitsNeeded(int value)
Find out number of bits needed to represent a positive integer 
return Integer.SIZE - Integer.numberOfLeadingZeros(value);
intcountBitsSet(int bitfield)
count Bits Set 
int count = 0;
for (short i = 0; i < Integer.SIZE; i++) {
    if ((bitfield & 0x01) != 0) {
        count++;
    bitfield >>>= 1;
return count;
...