Java集合的定义与Collection类使用详解

package com.collections;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
public class Demo01 {
    public static void main(String[] args) {
//        创建集合
        Collection collection = new ArrayList();
//        1.添加元素
        collection.add("苹果");
        collection.add("梨子");
        collection.add("榴莲");
        System.out.println(collection);
        System.out.println("元素个数为:"+collection.size());
//        2.删除元素
        collection.remove("榴莲");
        System.out.println(collection);
        System.out.println("元素个数为:"+collection.size());
//        3.遍历元素
//        3.1增强for循环
        System.out.println("-------------3.1增强for循环----------------");
        for (Object object:collection) {
            System.out.println(object);
        }
        System.out.println("-------------3.2使用迭代器Iterator----------------");
//        3.2使用迭代器Iterator,本身是一个接口
//        三种方法：hasNext()判断是否有元素，next()获取下一个元素,remove()删除元素
        Iterator it = collection.iterator();
        while (it.hasNext()){
           String s =  (String)it.next();
            System.out.println(s);
            //it.remove();
        }
        System.out.println("元素个数为"+collection.size());
//        4.判断：contains
        System.out.println(collection.contains("西瓜"));
//        判断是否为空
        System.out.println(collection.isEmpty());
    }
}

package com.collections.test;
public class Student {
    private String name;
    private int age;
    public Student() {
    }
    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

package com.collections.test;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
public class Demo01 {
    public static void main(String[] args) {
        Student s1 = new Student("aaa",18);
        Student s2 = new Student("bbb",19);
        Student s3 = new Student("ccc",20);
        Collection collection = new ArrayList();
        collection.add(s1);
        collection.add(s2);
        collection.add(s3);
        System.out.println("元素个数为："+collection.size());
        System.out.println(collection.toString());
//        collection.remove(s1);
//        collection.remove(new Student("ccc",20));
        System.out.println("删除后："+collection.size());
        System.out.println(collection.toString());
//        3.遍历
        for (Object object:collection) {
            Student s = (Student)object;
            System.out.println(s);
        }
        System.out.println("-----------------------------------------");
//        迭代器
        Iterator it = collection.iterator();
        while(it.hasNext()){
             Student s = (Student) it.next();
            System.out.println(s);
        }
    }
}