What is the difference between & and && in java

The difference between & and && in java: 1. When the && operator operates, when the value of the first expression is false, the second expression will not be calculated; while the & operator Then both expressions will be executed regardless of whether the value of the first expression is true. 2. The & operator can be used as a bitwise operator, but the && operator cannot.

The operating environment of this tutorial: windows7 system, java8 version, DELL G3 computer.

In Java, && and & are both logical operators representing "and", which means and. They are all true when the expressions on both sides are true, and the entire operation result is true, otherwise it is false. Next, in the article, we will introduce the differences between the two in detail.

The difference between & and &&

& and && are both logical operators, but && is also called a short-circuit operator. Because when the value of the first expression is false, the second expression will not be evaluated;

and & will execute both expressions regardless of whether the first expression is true. In addition, & can also be used as a bitwise operator. When the expressions on both sides of & are not of Boolean type, & represents a bitwise operation.

&& Operation

int i = 0;        
if(i == 3  && ++i > 0 )
 {
 }
System.out.println("i = " + i);

The result is:

i = 0

Cause: The second expression is not executed

& The result of the operation

 int i = 0;        
 if(i == 3  & ++i > 0 )
  { 
  }
  System.out.println("i = " + i);

is:

i = 1

The second expression performs the

expansion Knowledge: Logical operators

Logical operators connect the relational expressions of various operations to form a complex logical expression to determine whether the expression in the program is true and the result of the determination Is true or false.

Logical operators operate on Boolean variables, and their results are also Boolean, as shown in Table 1.

##&&a&&bShort circuit and When ab is all true, the calculation result is true, otherwise it is false. 2>1&&3true##||##!!alogical NOTWhen a is true, the value is false, when a is false, the value is true!(2>4)true|a|bLogical ORWhen ab is all false, the calculation result is false, otherwise it is true1>2| 3>5false&a&blogical logic and ab are both true, The calculation result is true, otherwise it is false1true#|| | Difference: If a is true, b is not calculated (because no matter what the value of b, the result is true)

Table 1 Usage, meaning and examples of logical operators

Operator	Usage	Meaning	Explanation	Example	Result
a||b	short circuit or	When ab is all false, the calculation result is false, otherwise it is true.	24	false

• Note: short-circuit AND (&&) and short-circuit OR (||) Ability to adopt optimized calculation methods to improve efficiency. In actual programming, short-circuit AND and short-circuit OR should be given priority.

Variables or expressions whose results are of boolean type can be combined into logical expressions through logical operators. Logical operators &&, || and ! Perform logical operations according to Table 2.

Table 2 Use logical operators to perform logical operations

b##truetruetruetruefalse falsetruefalsetruetruetruefalsefalsetruefalsefalsefalsefalsefalsetrue

逻辑运算符的优先级为：！运算级别最高，&& 运算高于 || 运算。！运算符的优先级高于算术运算符，而 && 和 || 运算则低于关系运算符。结合方向是：逻辑非（单目运算符）具有右结合性，逻辑与和逻辑或（双目运算符）具有左结合性。

下面是一些使用逻辑运算符的示例。

x>0 && x<=100    // 第一行语句
y%4==0 || y%3==0    // 第二行语句
!(x>y)    // 第三行语句

其中，第一行语句用于判断 x 的值是否大于 0 且小于或等于 100，只有两个条件同时成立结果才为真（true）。第二行语句用于判断 y 的值是否能被 4 或者 3 整除，只要有一个条件成立，结果就为真（true）。第三行语句先比较 x 和 y，再将比较结果取反，即如果 x 大于 y 成立，则结果为假（false），否则为真（true）。

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a

a&&b	a ||b	!a

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