What are the loop statements in java

There are three main loop structures in Java:

while loop

do...while loop

for loop

The program statements of the sequential structure can only be executed once. If you want to perform the same operation multiple times, you need to use a loop structure.

1. While loop

Syntax:

　　while( 布尔表达式 ) {
　　　　//循环内容
　　}

As long as it matches the Boolean expression, that is, the expression result is true, the loop will continue to execute.

Example:

Running result:

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2. do...while loop

For the while statement, if the conditions are not met, the loop cannot be entered. But sometimes we need to execute it at least once even if the conditions are not met.

The do…while loop is similar to the while loop. The difference is that the do…while loop will be executed at least once.

Syntax:

　　do{
　　　　//代码语句
　　　}while(布尔表达式);

Note: The Boolean expression is after the loop body, so the statement block has been executed before detecting the Boolean expression. If the Boolean expression evaluates to true, the block of statements executes until the Boolean expression evaluates to false.

Example:

Run result:

##3. for loop

Although all loop structures can be expressed with while or do...while, Java provides another statement - the for loop, which makes some loop structures simpler.

The number of times the for loop is executed is determined before execution.

Syntax:

　　for(初始值;布尔表达式;更新){
　　　　//代码语句
　　}

There are several instructions for the for loop:

The initialization step is executed first. A type can be declared, but one or more loop control variables can be initialized, or it can be an empty statement. Then, test the value of the Boolean expression. If true, the loop body is executed. If it is false, the loop terminates and execution of the statements following the loop body begins. After executing the loop once, update the loop control variables. Check the Boolean expression again. Perform the above process in a loop.

Example:

Run result:

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