练习题1

简单的Java有关数组、循环的练习题

知识点：数组、循环、if、边界

创建100个学生对象，id编号为1-100 把编号可以大于60的归为二组，其它归为一组

知识点：switch

定义一个方法，给1-4其中一个数字，返回春夏秋冬字符串，不命中则返回 错误季节。

知识点：static、数组、循环

定义一个Dog类，里面含有age静态变量初始值为10，有一个name成员属性，有一个changAge方法，使age自增1，创建含5个的dog数组，获取数组角标为3的dog对象，调用两次changAge方法，最后打印5个dog对象的age分别为多少？

public class AnswerTest {

    public static void main(String [] args){
       // test1();

        //test2();
        test3();
    }

    public static void test3(){
        Dog [] dogs = new Dog[5];

        for(int i=0; i<5; i++){
            Dog dog = new Dog();
            dog.setName("旺财"+i);
            dogs[i] = dog;
        }

        Dog dog =  dogs[3];
        dog.changeAge();
        dog.changeAge();

        for (Dog d : dogs){
            System.out.println("名称="+d.getName() + ", age="+d.getAge());
        }


    }

    public static void test2(){
        int season = 10;

        String content;

        switch (season){
            case 1:content="春";
                break;

            case 2:content="夏";
                break;

            case 3:content="秋";
                break;

            case 4:content="冬";
                break;

            default: {
                content="错误季节";
                System.out.println("default 执行");
            }
        }

        System.out.println(content);

    }

    public static void test1(){
        Student[] arr1 = new Student[60];
        int arr1Index = 0;

        Student[] arr2 = new Student[40];
        int arr2Index = 0;

        for(int i=0; i<100; i++){
            int num = i+1;
            Student student = new Student();
            student.setId(num);
            if(num > 60){
                arr2[arr2Index] = student;
                //arr2Index = arr2Index +1;
                arr2Index++;
            }else {
                arr1[arr1Index] = student;
                arr1Index++;
            }
        }


        for(Student s: arr1){
            System.out.println(s.getId());
        }

        System.out.println("============");
        for(Student s: arr2){
            System.out.println(s.getId());
        }

    }
}
public class Student {

    private int id;

    public int  getId(){
        return id;
    }

    public void setId(int id){
        this.id = id;
    }
}

public class Dog {

    public static int age =10;

    private String name;

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

    public String getName(){
        return name;
    }

    public void changeAge(){
        age++;
    }

    public int getAge(){
        return age;
    }

}

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