Operator explanation

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One 、 Arithmetic operator

1、 Definition

Arithmetic operators operate on numeric variables

2、 Introduction to arithmetic operators

3、 modulus % The essence of

% It's used to take the remainder , Can only be used in integers
modulus a%b The essence is ：
a % b = a - a / b * b

  10 % 3 => - 10 - (- 10) / 3 * 3 = - 10 + 9 = - 1
  10 % -3 = 10 - 10 / (-3) * (-3) = 10 - 9 = 1
  10 % -3 =    (- 10) - (- 10) / (-3) * (-3) = - 10 + 9 = - 1

4. Self increasing ++

front ++： First self increment and then assignment
after ++： Assign value first, then add value

int j = 8;
int k = ++j; // Equivalent j=j+1;k=j;
int k = j++; // Equivalent k =j;j=j+1;

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Two 、 Relational operator

1、 Definition

1. The result of relational operators is boolean type , That is, either true , Or false
2. Relationship expression Often used in if In the condition of a structure or in the condition of a cyclic structure

2、 Introduction to relational operators

3、 Details

1. The result of relational operators is boolean type , That is, either true , Or false.
2. The expression made up of relational operators , We call it relational expression . a > b
3. Comparison operator "==“ It can't be written by mistake ”="

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3、 ... and 、 Logical operators

1、 Definition

Used to connect multiple conditions （ Multiple relational expressions ） , The end result is also a boolean value .

2、 Introduction to logical operators

1. Short circuit and && , Short circuit or || , Take the opposite !
2. Logic and & , Logic or | ,^ Logical XOR
   

3、 Operational rules

  
1)   a&b : &   It's called logic and ：  The rules ：  When  a   and  b   Also for  true , The result is  true,   Otherwise  false
2)   a&&b : &&   It's called short circuit and ：  The rules ：  When  a   and  b   Also for  true , The result is  true, Otherwise  false
3)   a|b : |   It's called logic or , The rules ：  When  a   and  b  , There is one for  true , The result is  true, Otherwise  false

4)   a||b : ||   It's called short circuit or , The rules ：  When  a   and  b  , There is one for  true , The result is  true, Otherwise  false
5)    !a :   Call negative , Or non arithmetic . When  a   by  true,   The result is  false,   When  a   by  false  yes , The result is  true
6)   a^b:   It's called logical XOR , When  a   and  b   Different time , The result is  true,   Otherwise  false

about && Short circuit and , If the first condition is false , The latter condition is no longer to judge
about & Logically and logically , If the first condition is false , The latter conditions will still judge

Short circuit or ： If the first condition is true,
Then the second condition will not judge , The final result is true , Efficient
Logic or ： Whether or not the first condition is true , The second condition is to judge , Low efficiency

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Four 、 Assignment operator

1、 Definition

An assignment operator is the value of an operation , Assign to the specified variable .

2、 Introduction to assignment operators

Basic assignment operators = int a = 10;
Compound assignment operator
+= ,-= ,*= , /= ,%= etc. ,
a += b; [ Equivalent a = a + b; ]
a -= b; [ Equivalent a = a - b; ]

3、 Characteristics of assignment operators

1. The order of operation is from right to left int num = a + b + c;
2. To the left of the assignment operator It can only be a variable , On the right It could be a variable 、 expression 、 Constant values int num = 20; int num2= 78 * 34 - 10; int num3 = a;
3. The compound assignment operator is equivalent to the following effect such as ： a+=3; Equivalent to a=a+3; Other analogies
4. The compound assignment operator performs type conversion . byte b = 2; b+=3; b++;

 byte b = 3;
 b += 2;     Equivalent  b = (byte)(b + 2); 
 b++;   b = (byte)(b+1);

5、 ... and 、 Ternary operator

1. Basic grammar

Conditional expression ? expression 1: expression 2;
Operational rules ：

1. If the conditional expression is true , The result of the operation is an expression 1;
2. If the conditional expression is false , The result of the operation is an expression 2;

2. Use details

1. expression 1 And expressions 2 Type that can be assigned to the receiving variable ( Or it can be automatically converted )
2. The ternary operator can be converted to if–else sentence

int res = a > b ?    a++ :    --b;
if ( a > b) res = a++;
else res = --b;

// Ternary operator details 

public class TernaryOperatorDetail {
    	

// Write a  main  Method 
public static void main(String[] args) {
    
// expression  1  And expressions  2  Type that can be assigned to the receiving variable 
//( Or it can be automatically converted / Or cast )
int a = 3;
int b = 8;
int c = a > b ? (int)1. 1 : (int)3.4;// Tolerable 
double d = a > b ? a : b + 3;// Tolerable , Satisfy  int -> double
}
}

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