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增强for循环（也称for each循环）是JDK1.5以后出来的一个高级for循环，专门用来遍历数组和集合。
它的内部原理其实是个Iterator迭代器，所以在遍历的过程中，不能对集合中的元素进行增删操作
增强for循环 基本语法
for(元素类型 变量名：集合名或数组名){

}

使用三种不同循环遍历List<Student>
1.传统for循环
2.迭代器Iterator
3.增强for循环 底层基于迭代器Iterator

package com.xd;import java.util.ArrayList;public class Test {public static void main(String[] args) {// 增强for循环 for each 遍历 数组和集合int[] arr = new int[]{60,70,50,90};for (int i = 0; i < arr.length; i++) {System.out.println(arr[i]);}for (int j : arr) {System.out.println(j);}String[] strs = {"01","02","03"};for (String str : strs) {System.out.println(str);}ArrayList<String> arrayList = new ArrayList<>();arrayList.add("01");arrayList.add("02");arrayList.add("03");for (String str:arrayList){System.out.println(str);}}
}

package com.xd;import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;public class Test02 {public static void main(String[] args) {List<Student> students = new ArrayList<>();students.add(new Student("a",1));students.add(new Student("b",2));students.add(new Student("c",3));// 方式一遍历 集合for (int i=0;i<students.size();i++){Student student = students.get(i);System.out.println(student.getName() + "," + student.getAge());}// 方式二遍历 迭代器遍历集合Iterator<Student> iterator = students.iterator();while (iterator.hasNext()) {Student student = iterator.next();System.out.println(student.getName() + "," + student.getAge());}// 方式三 增强for循环 foreachfor (Student stu:students) {System.out.println(stu.getName() + "," + stu.getAge());}}
}