Java 循环之 for 语句
Java 语言的 for 循环语句是一个循环控制结构，可以执行指定次数的循环
Java 语言提供了三种循环结构，前面我们已经学习了 while 和 do...while
第三种是 for 循环，它可以让一些循环结构变得更加简单
for 循环执行的次数是在执行前就确定的
语法
for(初始化; 布尔表达式; 更新) {
// 代码语句
}
最先执行初始化步骤，可以声明一种类型，但可初始化一个或多个循环控制变量，也可以是空语句
然后，检测布尔表达式的值
如果为 true，循环体被执行
如果为 false，循环终止，开始执行循环体后面的语句
执行一次循环后，更新循环控制变量
再次检测布尔表达式，循环执行上面的过程
Java for 循环语句流程图
image.png
范例
public class Test {
public static void main(String args[]) {
for(int x = 10; x < 20; x = x+1) {
System.out.print("value of x : " + x );
System.out.print("\n");
}
}
}
编译运行以上 Java 代码，输出结果如下
value of x : 10
value of x : 11
value of x : 12
value of x : 13
value of x : 14
value of x : 15
value of x : 16
value of x : 17
value of x : 18
value of x : 19
## Java 增强 for 循环
Java 还有一种主要用于数组的增强型 for 循环
Java 增强 for 循环语法格式如下
for(声明语句 : 表达式)
{
// 代码句子
}
1. **声明语句** 声明新的局部变量，该变量的类型必须和数组元素的类型匹配
其作用域限定在循环语句块，其值与此时数组元素的值相等
2. **表达式** 是要访问的数组名，或者是返回值为数组的方法
### 范例
public class Test {
public static void main(String args[]){
int [] numbers = {10, 20, 30, 40, 50};
for(int x : numbers ){
System.out.print( x );
System.out.print(",");
}
System.out.print("\n");
String [] names ={"James", "Larry", "Tom", "Lacy"};
for( String name : names ) {
System.out.print( name );
System.out.print(",");
}
}
}
编译运行以上 Java 代码，输出结果如下
10,20,30,40,50,
James,Larry,Tom,Lacy,
[← Java 循环之 do...while 语句](/l/yufei/java/java-basic-dowhile.html)[Java break 语句 →](/l/yufei/java/java-basic-break.html)
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