Java 集合 之 List

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/** * 注意: 1. ArrayList 是按照添加的顺序,有序先进先出的. 2. ArrayList 可以添加重复元素 3. ArrayList 也可以添加 空值 null 4. ArrayList 内部是以对象数组 实现的 */ import java.util.ArrayList; import java.util.List; public class Test { public static void main(String[] args) { List list = new ArrayList(); // boolean add(Object o) list.add(1); list.add(1); list.add(null); list.add(2.5); list.add(true); list.add("王强"); list.add('A'); list.add(new Cat("波斯猫")); // // Object get(int index) Object wangqiang = list.get(3); System.out.println(wangqiang); // int size() System.out.println(list.size()); // // boolean contains(Object o) System.out.println(list.contains("王强")); // boolean isEmpty() System.out.println(list.isEmpty()); // // set(int index, Object element) list.set(4, 'B'); System.out.println(list.get(4)); // //遍历集合打印所以元素 for (int i = 0; i < list.size(); i++) { Object obj = list.get(i); System.out.print(obj + ","); } // boolean remove(int index) list.remove(4); System.out.println(""); for (int i = 0; i < list.size(); i++) { Object obj = list.get(i); System.out.print(obj + ","); } // void clear() list.clear(); System.out.println(""); System.out.println(list.size()); System.out.println(list.isEmpty()); for (int i = 0; i < list.size(); i++) { Object obj = list.get(i); System.out.print(obj + ","); } } } public class Cat { private String name; public Cat(String name) { this.name = name; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String toString() { return name; } } 

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