java 面向对象练习 1

1

public class Person {
    public String name;
    public int age;
    public String sex;

    public void study(){
        System.out.println("studying");
    }

    public void showAge() {
        System.out.println("age:"+age);
    }

    public int addAge(int i){
        age += i;
        return age;
    }

}

public class PersonTest {
    public static void main(String[] args) {
        Person p1=new Person();
        p1.age=26;
        p1.name="azai";
        p1.sex="f";

        p1.study();
        p1.showAge();
        int newage=p1.addAge(2);
        System.out.println(newage);
    }
}

2.设计cricle类计算圆得面积

public class CircleTest{
    public static void main(String[] args) {
        Circle c=new Circle();
        Scanner sc=new Scanner(System.in);
        System.out.println("输入半径：");
        c.r=sc.nextInt();
        double area=c.Area(c.r);
        System.out.println(area);
    }
}

class Circle{
    int r;
    public double Area(int r){
        double s=Math.PI *r*r;
        return s;
    }
}

3.矩阵

1.声明一个方法打印一个10*8的矩阵

 2.修改方法，继续计算矩阵的面积

 3.修改方法，提供m*n两个参数，打印一个m*n的矩阵,计算矩阵的面积

public class Test {
    public static void main(String[] args) {
        Test t=new Test();
        t.method1();
        t.method2();
        Scanner sc=new Scanner(System.in);
        int m=sc.nextInt();
        int n=sc.nextInt();
        t.method3(m, n);
    }
//1
    public void method1(){
        for (int i = 0; i <10; i++) {
            for (int j = 0; j < 8; j++) {
                System.out.print("* ");
            }
            System.out.println(" ");
        }

    }
//2
    public void method2(){
        int area=8*10;
        System.out.println(area);

    }
//3
    public void method3(int m,int n){
        for (int i = 0; i  
4.类：Student
 
属性:number state score
 
20个学生对象，年级，成绩随机
 
 
1.打印出3年级的学生信息
 
2.使用冒泡排序学生成绩，并遍历所有学生信息
 
public class Test4 {
    public static void main(String[] args) {
        Student[] s=new Student[20];//定义学生类数组储存学生信息
        for (int i = 0; i < s.length; i++) {
            //给数组元素赋值
            s[i]=new Student();
            //给s对象的属性赋值
            s[i].number=(i+1);
            Random r=new Random();
            s[i].state=r.nextInt(3)+1;
            s[i].score=r.nextInt(100);
        }
        Test4 test=new Test4();//定义测试类对象，调用测试类方法
        test.show(s);
        test.State3(s);
        test.sort(s);
    }

    public void show(Student[] s){
        for (int i = 0; i < s.length; i++) {
            System.out.println("学号tt年级tt分数tt");
            System.out.println(s[i].number+"tt"+s[i].state+"tt"+s[i].score+"tt"); 
        }
    }
    public void State3(Student[] s){
         System.out.println("三年级信息");
         for (int i = 0; i < s.length; i++) {
             if(s[i].state==3){
                 System.out.println("学号tt年级tt分数tt");
                 System.out.println(s[i].number+"tt"+s[i].state+"tt"+s[i].score+"tt");
             }
         }
    }

    public void sort(Student[] s) {
        System.out.println("排名");
        for (int i = 0; i < s.length-1; i++) {
            for (int j = 0; j < s.length-i-1; j++) {
                if(s[j].score