列表 List
list元素添加和移除
public class List1 {
@Test
public void f(){
List list = new LinkedList();
list.add(1);
list.add(1);
list.add("abc");
list.add("abc");
list.add(false);
System.out.println(list.contains("abc")); //true
list.remove("abc"); // 移除
System.out.println(list.contains("abc"));//true
list.remove("abc");
System.out.println(list.contains("abc"));//false
}
@Test
public void f1() {
LinkedList list = new LinkedList();
list.addFirst("100");
list.addFirst("200");
list.addFirst("300");
list.addFirst("400");
for (int i=0;i < list.size();i++){
System.out.println(list.get(i)); // 400 300 200 100
}
}
}
练习:List集合元素替换
七、向list集合添加姓名{张三,李四,王五,二丫,钱六,孙七},将二丫替换为王小丫。
List集合元素替换
@Test
public void list01(){
//在java中,所有的工具类都是以s结尾, Arrays Collections
List<String> list = new ArrayList<>(); //LinkedList();
Collections.addAll(list,"张三","李四","王五","二丫","钱六","孙七");
/*list.add("张三");
list.add("李四");
list.add("王五");
list.add("二丫");
list.add("钱六");
list.add("孙七");*/
// 替换元素
list.set(3,"王小丫");
/*int index = list.indexOf("二丫");
list.set(index, "王小丫");*/
//输出
//System.out.println(list);
for (String s : list) {
System.out.println(s);
}
}