BitOperations.java

publicclassBitOperations {
//Get ith Bit
publicstaticintgetIthBit(intn, inti) {
intbitMask = 1<<i;
return (n & bitMask) == 0 ? 0 : 1;
 }

//Set ith Bit
publicstaticintsetIthBit(intn, inti) {
intbitMask = 1<<i;
returnn | bitMask;
 }

//Clear ith Bit
publicstaticintclearIthBit(intn, inti) {
intbitMask = ~(1<<i);
returnn & bitMask;
 }

//Update ith Bit
publicstaticintupdateIthBit(intn, inti, intval) {
//Method1
// if(val == 0) {
// return n & (~(1<<i));
// } else {
// return n | (1<<i);
// }

//Method2
n = clearIthBit(n, i);
intbitMask = val<<i;
returnn | bitMask;
 }

//Clear Last i Bits
publicstaticintclearLastIbits(intn, inti) {
intbitMask = (~0)<<i; // or (-1)<<i
returnn | bitMask;
 }

//Clear Bits in Range (i,j)
publicstaticintclearBitsinRange(intn, inti, intj) {
inta = ~0<<i;
intb = (1<<i)-1;
intbitMask = a | b;
returnn & bitMask;
 }

//Check if number is power of 2 or not
publicstaticbooleanisPowerof2(intn) {
return (n & (n-1)) == 0;
 }

//Count number of set bits
publicstaticintcountSetBits(intn) {
intsetBits = 0;
intbitMask = 1;
while(n != 0) {
if((n & bitMask) != 0) { //last bit is 1
setBits++;
 }
n = n>>1;
 }
returnsetBits;
 }

//a faster method to count set bits
publicstaticintcountSetBits2(intn) {
intsetBits = 0;
while(n>0) {
// removes the last set bit from curr number
n = n & (n-1); 
setBits++;
 }
returnsetBits;
 }
publicstaticvoidmain(Stringargs[]) {
System.out.println(countSetBits(9)); 
 }
}