package com.zzp.demo; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; /** * * 泛型的使用 * @author java * */ public class TestGeneric { public static void main(String[] args) { // TODO Auto-generated method stub MyCollection<String> mc = new MyCollection<String>(); mc.set("dhfjs", 0); String b = (String) mc.get(0); System.out.println("b:"+b); List list = new ArrayList(); Map map = new HashMap(); } } class MyCollection<E>{ Object[] objs = new Object[5]; public void set(E e,int index){ objs[index] = e; } public E get(int index){ return (E)objs[index]; } }
package com.zzp.demo; import java.util.ArrayList; import java.util.Collection; import java.util.List; /** * * 测试collection中的方法 * @author java * */ public class TestList { public static void main(String[] args) { test03(); } public static void test01(){ Collection<String> c = new ArrayList<>(); System.out.println(c.size()); System.out.println(c.isEmpty()); c.add("张三"); c.add("张四"); System.out.println(c); System.out.println(c.size()); c.contains("张三"); Object[] a = c.toArray(); c.remove("张四"); System.out.println(c); c.clear(); System.out.println(c.size()); } public static void test02(){ List<String> list01 = new ArrayList<>(); list01.add("aa"); list01.add("bb"); list01.add("cc"); List<String> list02 = new ArrayList<>(); list02.add("aa"); list02.add("dd"); list02.add("ee"); System.out.println("list01:"+list01); list01.addAll(list02); System.out.println("list01:"+list01); list01.removeAll(list02); System.out.println("list01:"+list01); list01.retainAll(list02); System.out.println("list01:"+list01); System.out.println(list01.contains(list02)); } public static void test03(){ List<String> list = new ArrayList<>(); list.add("A"); list.add("B"); list.add("C"); list.add("D"); System.out.println(list); list.add(2, "张三"); System.out.println(list); list.remove(2); System.out.println(list); list.set(2, "李四"); System.out.println(list); System.out.println(list.get(0)); list.add("C"); list.add("B"); list.add("A"); System.out.println(list); System.out.println(list.indexOf("A")); System.out.println(list.lastIndexOf("A")); System.out.println(list.indexOf("张三")); System.out.println(list.lastIndexOf("张三")); } }