一文掌握Java中List和Set接口的基本使用

public class Test {
        public static void main(String[] args) {
            List list = new ArrayList();
            list.add(66);
            list.add(5);
            list.add(77);//66 5 77
    
            list.add(2,44);//66 5 44 77
    
            List list2 = new ArrayList();
            list2.add(2);
            list2.add(1);
    
            list.addAll(list2);//66 5 44 77 2 1
            list.addAll(1, list2);//66 2 1 5 44 77 2 1
    
            System.out.println("清空之前："+list.size());
           // list.clear();
           // System.out.println("清空之后："+list.size());
            System.out.println(list.contains(5));//t
            System.out.println(list.containsAll(list2));//t
    
            List list3 = new ArrayList();
            list3.add(66);
            list3.add(77);
            list3.add(88);
            System.out.println(list.containsAll(list3));//f
    
            System.out.println(list.get(3));//5
    
            System.out.println(list.indexOf(88));//-1
            System.out.println(list.lastIndexOf(2));//6
    
            //list.clear();
            System.out.println(list.isEmpty());
            List list4=null;
            //System.out.println(list4.isEmpty()); 空指针异常
    
            System.out.println(list.remove(3));//66 2 1 44 77 2 1
            // System.out.println(list.remove(2));
    
            list.set(1, 88);//66 88 1 44 77 2 1
    
            Object[] os=list.toArray();
            for(int i=0;i<os.length;i++){
                System.out.print(os[i]+" ");
            }
            System.out.println();
        }
    }

 for (int i = 0; i < 集合名.size(); i++) {
       //i代表当前下标
       //通过集合名.get(i)的方式获取当前元素
   }
   如：
 for (int i = 0; i < list.size(); i++) {
        System.out.print(list.get(i)+" ");
         }
        System.out.println();

//获取迭代器对象
Iterator it=集合名.iterator();
while(it.hasNext()){//集合存在下一元素则继续后续操作
//通过it.next()使指针后移，得到元素
}
如：
Iterator it=list.iterator();
while(it.hasNext()){
System.out.print(it.next()+" ");
}
System.out.println();

for (Object o: list) {
System.out.print(o+" ");
}
System.out.println();

 //lambda简化
         集合名.forEach(o-> {o就代表当前元素});
 如：
         list.forEach(new Consumer() {
             @Override
             public void accept(Object o) {
                 System.out.print(o + " ");
             }
         });
         System.out.println();
 
         // lambda
         list.forEach(o-> System.out.print(o+" "));

List<Integer> list = new ArrayList<Integer>();
        list.add(66);
        list.add(88);
       
        list.forEach(new Consumer<Integer>() {
            @Override
            public void accept(Integer i) {
                System.out.println(i);
            }
        });

          public class Test2 {
            public static void main(String[] args) {
                Set<Student> set = new TreeSet<Student>(new Comparator<Student>() {
                    @Override
                    public int compare(Student o1, Student o2) {
                        //根据学生年龄从大到小排序
                        return o2.getAge()-o1.getAge();
                    }
                });
                set.add(new Student("张三", 20));
                set.add(new Student("lisi", 21));
                set.add(new Student("lisi", 21));
                set.add(new Student("wangwu", 22));
                set.add(new Student("maliu", 19));
                set.forEach(s-> System.out.println(s));
            }
        }