<< 在 Java 中是什么意思？

Question

I can't find out what << means in Java because I can't search for it on Google - I am absolutely lost!

The code in question is:

public int getRGB() {
    return ((red << 16) | (green << 8) | blue);
}

It's taken from: http://java.sun.com/docs/books/tutorial/essential/concurrency/example/ImmutableRGB.java

I would really appreciate someone telling me, thanks!

Answer 1

Left shift of the bits

If red == 4 (which in binary is: 00000100) then red << 16 will insert sixteen 0-bits at its right, yielding: 000001000000000000000000 which is 262144 in decimal

Answer 2

Q. What is this?
A. An "operator"

Q. How do I get to know about operators in java?
A. Google for "Java operators"

And the result is this :

The signed left shift operator "<<" shifts a bit pattern to the left, and the signed right shift operator ">>" shifts a bit pattern to the right. The bit pattern is given by the left-hand operand, and the number of positions to shift by the right-hand operand. The unsigned right shift operator ">>>" shifts a zero into the leftmost position, while the leftmost position after ">>" depends on sign extension.

Answer 3

Left shift a number of bits. It is equivalent to multiplying by two that many times.

It's used for setting specific bits in a byte, or specific bytes in a word.

Answer 4

It is the left shift operator. Here's some more information on shift operators from the Java Tutorial .

In your example code the three integer values: red, green and blue will typically have values 0-255. Hence, it is possible to combine these values and represent them as a single integer by shifting the red value by 16 bits, shifting the green value by 8 bits and then performing a bitwise-OR operation to combine the values.

Answer 5

its a bit shift. search for operators java , it will return you detailed explanations.

Answer 6

它是一个左移

Answer 7

它的左移并将红、绿、蓝转换为 24 位数字

Answer 8

"<<" means left shift the bits of a value.
">>" means right shift the bits of a value.

example:
int a = 5; //the binary value of 5 is 101
a = a << 3; //left shift 3 bits on 101, 101 000<< add 3 bits(0) on the right, become '101000'
System.out.println(a); //this will display 40, the decimal for '101000'

int b = 9; //the binary value of 8 is 1001
b = b >> 3; //right shift 3 bits on >>000 1 001 add 3 bits(0) on the left, truncate the last 3 bits on the right become '001'
System.out.println(b); //this will display 1, the decimal for '001'