Dark Horse Programmer--java Basics-operator, bit manipulation

------Java Training, Android training, iOS training,. NET training, look forward to communicating with you! -------

<pre name= "code" class= "Java" >public class test{public    static void Main (String args[]) {          byte b = 3;          B = B + 2;          System.out.println (b);}}

This code output is wrong, because byte accounted for a byte, no defined integer 2 accounted for 4 bits, b+2-phase enhancement to int type, and then assigned to B, but B only 1 bits, so will error, the correct code:

public class test{public    static void Main (String args[]) {          byte b = 3;          b = (int) (b + 2);          System.out.println (b);}}

The difference between 2.system.out.println and System.out.print is that the former contains a \ n transfer character and wraps itself.

Several escape characters common to Java:

\ n: Line break

\b: Backspace

\ t: tab, equivalent to table

\ r: Enter, equal to \ n

3. Operators

① arithmetic operator +,-,*,/,%

Emphasize two operators:/and%

eg

int x = 4250;

x = x/1000*1000;

The result is not 4250, but 4000.

The% operator cannot have decimals, and the sign of the result when remainder depends on the preceding number.

1%-5 = 1;

-1%5 =-1;

* It is good to avoid overflow when using the method operator.

Special emphasis is placed on the + + and--operator, a++,++a,b--,--b;

The operator is preceded by the assignment of a value, and in the following case it is assigned after the first operation.

②: Logical operators & | ^ ! &&| |

&& | | Also known as short-circuit operator

Differences between &&, &, | |, | operators: A (&&, &, | |, |) B

&& when A is false, B does not have to judge, | | When A is true, B does not have to judge, | and & whether A is true or False B is judged.

③: Link operator +

The + in Ava represents the link operator, and when the string is connected to any data, it eventually becomes a string.

④: Bitwise operators << >> ^ >>> & | !

>> signed Right Shift

>>> Unsigned Right Shift

The bitwise operator is computationally efficient, and when the same number is two times this value does not change, eg7^4^4=7.

Two number exchange:

Method One: Variable method

temp = A;

A = b;

b = temp;

Method Two:

A = a +b;

b = a A;

A = a-B;

Method Three:

A = a ^ b;

b = a^b;

A = A^b;

>> operator: If it is a negative number, then the highest bit of the bit is basically 1, of course, by the original highest bit, so the operation often uses >>>.

Take a minimum of four bits of a number with a minimum of four bits of &,eg:60 of 1100,

You can use 60&15, 0011 1100

0000 1111

------------------

0000 1100

If it is the second-to-last four-bit, you can take the lowest four, and then &, how to go, of course, the right SHIFT, >>> 4 & 15.

0011 1100

>>> 0000 0011

& 0000 1111

-------------------------

0000 0011

That's OK.

Dark Horse Programmer--java Basics-operator, bit manipulation