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Operator explanation
2022-07-05 00:26:00 【The learning path of Java Rookies】
Operator
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;
Two 、 Relational operator
1、 Definition
- The result of relational operators is boolean type , That is, either true , Or false
- 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
- The result of relational operators is boolean type , That is, either true , Or false.
- The expression made up of relational operators , We call it relational expression . a > b
- Comparison operator "==“ It can't be written by mistake ”="
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
- Short circuit and && , Short circuit or || , Take the opposite !
- 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
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
- The order of operation is from right to left int num = a + b + c;
- 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;
- The compound assignment operator is equivalent to the following effect such as : a+=3; Equivalent to a=a+3; Other analogies
- 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 :
- If the conditional expression is true , The result of the operation is an expression 1;
- If the conditional expression is false , The result of the operation is an expression 2;
2. Use details
- expression 1 And expressions 2 Type that can be assigned to the receiving variable ( Or it can be automatically converted )
- 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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