Java SE (20) operator-assignment operator

Assignment operator

Function: Assign the value of a constant, variable or expression to a variable.

species:

Operator	Calculation	example	result
=	Assignment	a=3;b=2;	a=3; b=2;
+=	Plus equals	a=3;b=2; a+=b;	a=a+b=5; b=2;
-=	Minus equal	a=3;b=2; a-=b;	a=a-b=1; b=2;
*=	Multiply equals	a=3;b=2; a*=b;	a=a*b=6; b=2;
/=	Divide equal	a=3;b=2; a/=b;	a=a/b=1; b=2;
%=	Modulo equal	a=3;b=2; a%=b;	a=a%b=1; b=2;

 

 

 

 

 

 

 

 

table of Contents

Assignment (=)

Extended assignment operator

Interview questions

---

• Assignment (=)

In the assignment process, the order of operations is from right to left , and the result of the expression on the right is assigned to the variable on the left.

Exercise:

public class TestOpe07{
	public static void main(String[] args){
		//任意给出两个数，交换两个数并输出
		//给出两个数
		int a=5;
		int b=10;
		//输出交换前的两个数
		System.out.println("交换前："+a+"\t"+b);
		//交换
		int t;   //引入一个中间变量
		t=a;
		a=b;
		b=t;
		//输出交换后的两个数
		System.out.println("交换后："+a+"\t"+b);
	}
}

operation result:

• Extended assignment operator

        When assigning values ​​to variables, when the two data types are incompatible with each other, or the value range of the target data type is smaller than the source type, a forced data type conversion is required. However, when the +=, -=, *=, /=, %= operators are used for assignment, the forced type conversion will be automatically completed , and the program does not need to make any explicit declarations . E.g:

public class TestOpe08{
	public static void main(String[] args){
		short s=3;
		int i=5;
		s+=i;    //相当于s=(short)(s+i)
	
		System.out.println("s="+s);
	}
}

operation result:

Note 1: The difference between a+=b and a=a+b:

a+=b Slightly poor readability High
compilation efficiency Low -level automatic type conversion a=a+b Good readability Low compilation efficiency Manual type conversion

• Interview questions

(1) Is a+=b equivalent to a=a+b, then is it also equivalent to a=b+a?

         For basic data type is the same . E.g:

              a=10；b=20;    

              a=a+b=30

              a=b+a=30

         For String type is not the same . E.g:

               a='x';b='u';

               a=a+b="xu"

               a=b+a="ux"

(2) Which sentence of the following code is wrong:

      byte a = 10; 
      int b = 20;  
      a + = b;  
      a = a + b ; // rectification a = (byte) (a + b);

• Error-prone:

In Java, multiple variables can be assigned through a single assignment statement. Specific examples are as follows:

int x,y,z;

x=y=z=5;      

It is important to note that the following writing method is not possible in Java.

int x=y=z=5; //This is wrong