集合迭代、for遍历、foreach遍历

集合迭代遍历

import java.util.Collection; import java.util.HashSet; import java.util.Iterator; public class ArrayTest { public static void main(String[] args) { //多态，创建集合对象 Collection c=new HashSet(); //添加元素 c.add("zs"); c.add(123); c.add(new Object()); //创建迭代器对象 Iterator it =c.iterator(); /** * Boolean hasNext()：如果仍有元素可以迭代，返回true * Object next():返回迭代下一个元素 */ while (it.hasNext()){ Object obj = it.next(); System.out.println(obj); } } }

for遍历

package com; import java.util.ArrayList; import java.util.List; public class test { public static void main(String[] args) { List a = new ArrayList(); a.add("zs"); a.add("lisi"); a.add("ww"); for (int i = 0; i < a.size(); i++) { System.out.println(a.get(i)); } } }

foreach遍历

package com; import java.util.ArrayList; import java.util.List; public class test { public static void main(String[] args) { List a = new ArrayList(); a.add("zs"); a.add("lisi"); a.add("ww"); for(Object result:a){ System.out.println(result); } } }

while循环修改为for循环方式

package com; import java.util.ArrayList; import java.util.Iterator; import java.util.List; public class test { public static void main(String[] args) { List a = new ArrayList(); a.add("zs"); a.add("lisi"); a.add("ww"); //while循环修改为for循环方式 for (Iterator<String> it2 = a.iterator(); it2.hasNext(); ) { String re = it2.next(); System.out.println(re); } } }