Java SE基础---集合

测试 

import java.util.ArrayList;
public class ArrayListDemo {
    public static void main(String[] args) {
        ArrayList array=new ArrayList();
        //或者ArrayList array=new ArrayList<>();
        array.add("天地");
        array.add("任我");
        array.add(1,"广阔");
        array.add(3,"傲游");
        //array.add(5,"索引越界报错");
        System.out.println(array);
    }
}

运行结果

求长度：数组.length，String类.length()方法，ArrayList集合.size()

 测试 

import java.util.ArrayList;
public class ArrayListDemo02 {
    public static void main(String[] args) {
        ArrayList array=new ArrayList();
        array.add("天地");
        array.add("广阔");
        array.add("疏又何妨");
        array.add("狂有何妨");

        array.remove("广阔");
        array.remove(0);//删索引为0 即删天地
        array.set(1,"虽千万人吾往矣");
        System.out.println(array.get(1));

        System.out.println(array);
    }
}

运行结果

学生类

public class Student {
    private String name;
    private int age;
    public Student(){}
    public Student(String name,int age){
        this.name=name;
        this.age=age;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getAge() {
        return age;
    }
}

测试

import java.util.ArrayList;

public class ArrayListDemo03 {
    public static void main(String[] args) {
        ArrayList array=new ArrayList();
        Student s1=new Student("唐三",18);
        Student s2=new Student("小舞",17);
        Student s3=new Student("比比东",50);
        array.add(s1);
        array.add(s2);
        array.add(s3);
        for (int i = 0; i 

运行结果