CODEWITHSUNDEEP
javabit-manipulation
ic3
ic3

Reputation: 7680

Get last set bit position for an int

Is there a fast way to get the last bit of an integer in Java. Can be both the bit at position 5 or an integer with only the 5'th bit.

65 -> 64 
11 -> 8 
13 -> 8

No negative numbers

It's a wording issue it's not the last bit but highest bit.

Upvotes: 1

Views: 1365

Answers (2)

Joop Eggen
Joop Eggen

Reputation: 109547

Dive in the javadoc, always worth it: Integer.highestOneBit.

assert 64 == Integer.highestOneBit(65);
assert 2 == Integer.bitCount(65);
assert 6 == 31 - Integer.numberOfLeadingZeros(65);

There is also numberOfTrailingZeros and so on.

Upvotes: 5

Konstantin Yovkov
Konstantin Yovkov

Reputation: 62864

You can use the Integer.toBinaryString() method, which will give you a string representation of the integer argument as an unsigned integer in base 2.

String binary = Integer.toBinaryString(value);
char lastBit = binary.charAt(0);

Upvotes: 1

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