Java escape character and binary conversion

One: Escape character

\ r means accept keyboard input, equivalent to press ENTER.

\ n indicates a line break.

\ t tab, equivalent to Table key

\b backspace key, equivalent to back Space

\ ' single quotation mark

\ ' double quotes

\ \ represents a diagonal cross

Note: The line break is another line, the carriage return is the beginning of a line, so we usually write a file carriage return should be exactly called carriage return line break

Second: The conversion of the binary

The representation of an integer constant: a binary representation (binary, octal, decimal, hexadecimal)

Conversions between the binaries:

decimal into binary: Divide the decimal by 2until the quotient is 0 , and the remainder is concatenated from the bottom to the binary.

Ten---->1010

Binary to decimal: Multiplies each bit of the binary by 2^n, N starts at 0 ,n adds one each time , and adds the result.

1001----" 1*2^0 +0*2^1 +0*2^2+1*2^3 = 9

Binary transposition octal:

way 1:2 binary ---> decimal ---> octal

Mode two: An octal equivalent of three binary for, will be binary three bit a split, calculated

010 100 101 = 245

swap binary to hexadecimal : (0-9) (A (ten)-F (15))

0000 1010 0101 = A5

Three: Bitwise operators

& ( with ): Both are 1 When I am one, the others are 0

| ( or ) : Both are 0 only when the 0 , the others are 1.

^ ( xor ): The difference between the two is 1, the same as 0

~ ( inverse ):0 becomes 1,1 becomes 0.

The representation of negative numbers: The highest bit of bits is 1, then this number is a negative.

1111-1111 1111-1111 1111-1111 1111-1111 : -1

0000 0000 0000 0000 0000 0000 0000 0000 : 0

-2:1111-1111 1111-1111 1111-1111 1111-1110

-3:1111-1111 1111-1111 1111-1111 1111-1101

-4:1111-1111 1111-1111 1111-1111 1111-1100

-5:1111-1111 1111-1111 1111-1111 1111-1011

-6:1111-1111 1111-1111 1111-1111 1111-1010

-7:1111-1111 1111-1111 1111-1111 1111-1001

0000-0000 0000-0000 0000-0000 0000-0111 = 7

1111-1111 1111-1111 1111-1111 1111-1001

rule: Negative number corresponding to the positive number-1 , take the inverse

negative number corresponding to the positive negation +1

Role: Data is encrypted

four: shift operator : operation on Bits

1.6.1 >> Right Shift

1.6.2 << left Shift

1.6.3 >>> unsigned Right shift

>> Right Shift

<< left Shift

>>> unsigned Right shift

Move Right:

System.out.println (6>>1); --->3 6/2 2*1

System.out.println (6>>2); --->1 6/4 2*2

System.out.println (6>>3); --->0 6/8 2*3

System.out.println (6>>4);

System.out.println (9>>1); --->4 9/2 2*1

System.out.println (9>>2); --->2 9/4 2*2

System.out.println (9>>3); --->1 9/8 2*3

System.out.println (9>>4);//--->0 9/16

System.out.println ( -6>>1); -6/2-->-3

rule: Shift the number of digits to the right by dividing by 2 How many times you need to move.

Move Left:

SYSTEM.OUT.PRINTLN ("----- This is the result of the left shift ----------");

System.out.println (6<<1); --->12 6*2 2*1

System.out.println (6<<2); --->24 6*4 2*2

System.out.println (6<<3); --->48 6*8 2*2*2

System.out.println (6<<4); ---->96 6*16 2*2*2*2

Ystem.out.println ( -6<<2);//--->-24

rule: How many digits to the left, multiply this number by 2 times.

>>> unsigned Right shift

System.out.println (6>>>1); 3

System.out.println (6>>>2); 1

System.out.println ( -6>>>2); 1073741822

function : increases the operation rate. Bit arithmetic is the fastest execution.

For example: calculate 2*8 in the quickest way

2<<3 = = 2*8 = 16

features : A number A and two the same number ^, the final result is still the original number a.

Java escape character and binary conversion