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.
Table 1 Usage, meaning and examples of logical operators
Operator
Usage
Meaning
Explanation
Example
Result
##&&
a&&b
Short circuit and
When ab is all true, the calculation result is true, otherwise it is false.
2>1&&3<4
true
##||
a||b
short circuit or
When ab is all false, the calculation result is false, otherwise it is true.
2<1||3>4
false
##!
!a
logical NOT
When a is true, the value is false, when a is false, the value is true
!(2>4)
true
|
a|b
Logical OR
When ab is all false, the calculation result is false, otherwise it is true
1>2| 3>5
false
&
a&b
logical logic and
ab are both true, The calculation result is true, otherwise it is false
1<2&3<5
true
#|| | Difference: If a is true, b is not calculated (because no matter what the value of b, the result is true)
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
其中，第一行語句用于判斷 x 的值是否大于 0 且小于或等于 100，只有兩個(gè)條件同時(shí)成立結(jié)果才為真（true）。第二行語句用于判斷 y 的值是否能被 4 或者 3 整除，只要有一個(gè)條件成立，結(jié)果就為真（true）。第三行語句先比較 x 和 y，再將比較結(jié)果取反，即如果 x 大于 y 成立，則結(jié)果為假（false），否則為真（true）。
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