1. Java provides operators to perform bitwise and bit shift operations on int type.
The operators discussed in the section are less commonly used, the intent is to simply make you aware that these operators exist.
2. Bitwise operators overview:
a & b |
and | 3 & 5 | 1 | 1 if both bits are 1. |
a | b |
or | 3 | 5 | 7 | 1 if either bit is 1. |
a ^ b |
xor | 3 ^ 5 | 6 | 1 if both bits are different. |
~a |
not | ~3 | -4 | Inverts the bits. |
n << p |
left shift | 3 <<< 2 | 12 | Shifts the bits of n left p positions. Zero bits are shifted into the low-order positions. |
n >> p |
right shift | 5 >> 2 | 1 | Shifts the bits of n right p positions. If n is a 2's complement signed number, the sign bit is shifted into the high-order positions. |
n >>> p |
right shift | -4 >>> 28 | 15 | Shifts the bits of n right p positions. Zeros are shifted into the high-order positions. |
3. Examples
1) "AND" example:
@Test public void andTest() { int i = 12; // i = 0000,0000,0000,0000,0000,0000,0000,1100 int j = -3; // -3 = ~2 -> ~0000,0000,0000,0000,0000,0000,0000,0010 -> 1111,1111,1111,1111,1111,1111,1111,1101 int k = i & j; // 0000,0000,0000,0000,0000,0000,0000,1100 & // 1111,1111,1111,1111,1111,1111,1111,1101 -> // 0000,0000,0000,0000,0000,0000,0000,1100 ->12 assertEquals(12, k); }
2) "OR" example:
@Test public void orTest() { int i = 12; // i = 0000,0000,0000,0000,0000,0000,0000,1100 int j = -32768; // -32768 = ~32767 -> ~0000,0000,0000,0000,0111,1111,1111,1111 -> // 1111,1111,1111,1111,1000,0000,0000,0000 int k = i | j; // 0000,0000,0000,0000,0000,0000,0000,1100 | // 1111,1111,1111,1111,1000,0000,0000,0000 -> // 1111,1111,1111,1111,1000,0000,0000,1100 -> // -(~1111,1111,1111,1111,1000,0000,0000,1100 + 1) -> // -( 0000,0000,0000,0000,0111,1111,1111,0100) -> -32756 assertEquals(-32756, k); }
3) "XOR" example:
@Test public void xorTest() { int i = 32756; // i = 0000,0000,0000,0000,0111,1111,1111,0100 int j = -32768; // -32768 = ~32767 -> ~0000,0000,0000,0000,0111,1111,1111,1111 -> // 1111,1111,1111,1111,1000,0000,0000,0000 int k = i ^ j; // 0000,0000,0000,0000,0111,1111,1111,0100 ^ // 1111,1111,1111,1111,1000,0000,0000,0000 -> // 1111,1111,1111,1111,1111,1111,1111,0100 -> // -(~1111,1111,1111,1111,1111,1111,1111,0100 + 1) -> // -( 0000,0000,0000,0000,0000,0000,0000,1100) -> -12 assertEquals(-12, k); }
4) "NOT" test
@Test public void notTest() { int i = -12; // ~11 -> // ~0000,0000,0000,0000,0000,0000,0000,1011 -> // 1111,1111,1111,1111,1111,1111,1111,0100 int j = ~i; // ~1111,1111,1111,1111,1111,1111,1111,0100 // 0000,0000,0000,0000,0000,0000,0000,1011 assertEquals(11, j); i = -32768; j = ~i; assertEquals(32767, j); i = 0XFFFFFFFF; j = ~i; assertEquals(0, j); }
5) "Left Shift" test:
@Test public void leftShiftTest() { int i = 12; // 0000,0000,0000,0000,0000,0000,0000,1100 int j = i << 1; // 0000,0000,0000,0000,0000,0000,0001,1000 assertEquals(24, j); i = 0X8000000F; // 1000,0000,0000,0000,0000,0000,0000,1111 j = i << 1; // 0000,0000,0000,0000,0000,0000,0001,1110 assertEquals(30, j); }
6) "Right Shift" test:
@Test public void rightShiftTest() { int i, j; i = 12; // 0000,0000,0000,0000,0000,0000,0000,1100 j = i >> 1; // 0000,0000,0000,0000,0000,0000,0000,0110 assertEquals(6, j); j = i >>> 1; // 0000,0000,0000,0000,0000,0000,0000,0110 assertEquals(6, j); i = 0X8000000F; // 1000,0000,0000,0000,0000,0000,0000,1111 j = i >> 1; // 1100,0000,0000,0000,0000,0000,0000,0111 assertEquals(0XC0000007, j); j = i >>> 1; // 0100,0000,0000,0000,0000,0000,0000,0111 assertEquals(0X40000007, j); }
4. P.S
1) The size of "int" in java is 32-bit that is 8-byte, thus we can represent that with 8 hex number.
2) The left most bit represents the sign, 0 for positive and 1 for negative.
3) There is no unsigned int/byte data type in java, and we can use "long" if needed.
Reference Links:
1) http://docs.oracle.com/javase/tutorial/java/nutsandbolts/op3.html
2) http://www.leepoint.net/notes-java/data/expressions/bitops.html
3) http://stackoverflow.com/questions/9854166/declaring-an-unsigned-int-in-java
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