重学java——Collection

package com.cn3;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Scanner;

public class ScoreDemo {
    public static void main(String[] args) {
//        Scanner sc = new Scanner(System.in);
//        System.out.println("Score:");
//        int i = sc.nextInt();
//
//        Score s = new Score();
//        try {
//            s.check(i);//check方法是在Score里面的呀~
//        } catch (Exception e) {
//            e.printStackTrace();
//        }
        Collection c = new ArrayList();
//        add
//        System.out.println(c.add("hello"));
//        System.out.println(c.add("hello"));
//        System.out.println(c.add("hello"));
        c.add("helllooo");
        c.add("java");
        c.add("wolrd");
//        alt+7 看方法的快捷键
//        移除字符串 没有remove成功也没有返回哎
//        c.remove("java"); 移除
//        c.clear();清空
//        System.out.println(c.isEmpty()); 是否为空
//        System.out.println(c.contains("helllooo"));查询
//        字符的个数
//        System.out.println(c.size());
//
//        System.out.println(c);
//        迭代器
        Iterator it = c.iterator();
//        System.out.println(it.next());
//        System.out.println(it.next());
//        System.out.println(it.next());
//        System.out.println(it.next());  NoSuchElementException

//          if (it.hasNext()){
//              System.out.println(it.next());
//          }
//         if (it.hasNext()){
//            System.out.println(it.next());
//         }
//         if (it.hasNext()){
//            System.out.println(it.next());
//         }
//         if (it.hasNext()){
//            System.out.println(it.next());
//        }
        while(it.hasNext()){
//            迭代器对象
//            System.out.println(it.next());
            String i = it.next();
            System.out.println(i);
        }

    }
}

collectio方法是会在until包下的需要导包

创建的规则

package com.cn4;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

public class CollectionDemo {
    public static void main(String[] args) {
        //创建collection对象
        java.util.Collection c= new ArrayList<>();
        //创建学生对象
        Student s = new Student("ty",16);
        Student s1 = new Student("q",12);
        Student s2 = new Student("w",13);
        //把学生添加到集合
        c.add(s);
        c.add(s1);
        c.add(s2);
        //遍历集合（迭代器）
        Iterator it = c.iterator();
        while(it.hasNext()){
            Student i = it.next();
            System.out.println(i);
            System.out.println(s.getName()+"-"+s.getAge());
        }
    }
}