案例

package com.Test;

public class Test01 {
    public static void main(String[] args) {
        Rectangle rectangle = new Rectangle(5,3);
        int permeter = rectangle.getPermeter();
        System.out.println("周长"+permeter);

        int area = rectangle.getArea();
        System.out.println("面积"+area);
    }
}


class Rectangle{
    private int length;
    private int width;

    /**
     * 获取周长的方法
     * @return
     */
    public int getPermeter(){
        return this.length*2 + this.width*2;
    }

    /**
     * 获取面积的方法
     * @return
     */
    public int getArea(){
        return this.length * this.width;
    }


    public Rectangle(int length, int width) {
        this.length = length;
        this.width = width;
    }
    public Rectangle() {


    }

    @Override
    public String toString() {
        return "Rectangle{" +
                "length=" + length +
                ", width=" + width +
                '}';
    }

    public int getLength() {
        return length;
    }

    public void setLength(int length) {
        this.length = length;
    }

    public int getWidth() {
        return width;
    }

    public void setWidth(int width) {
        this.width = width;
    }
}



2.封装一个学生类，有姓名，年龄，性别，英语成绩，数学成绩，语文成绩，封装方法，求总分，平均分，以及打印学生的信息

public class StudentTest {
    public static void main(String[] args) {
        Student student = new Student("张三",17,"男",97,98,99);
        System.out.println(student.getName()+"的平均分="+student.avg());
        System.out.println(student.getName()+"的总分="+student.sum());

        System.out.println(student.toString());

    }
}

class Student{
    private String name;
    private int age;
    private String sex;
    private double score1;
    private double score2;
    private double score3;

    public double sum(){
        return this.score1 + this.score2 + this.score3;
    }

    public double avg(){
        return (this.score1 + this.score2 + this.score3)/3;
    }


    public Student() {

    }

    public Student(String name, int age, String sex, double score1, double score2, double score3) {
        this.name = name;
        this.age = age;
        this.sex = sex;
        this.score1 = score1;
        this.score2 = score2;
        this.score3 = score3;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                ", score1=" + score1 +
                ", score2=" + score2 +
                ", score3=" + score3 +
                '}';
    }

    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;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public double getScore1() {
        return score1;
    }

    public void setScore1(double score1) {
        this.score1 = score1;
    }

    public double getScore2() {
        return score2;
    }

    public void setScore2(double score2) {
        this.score2 = score2;
    }

    public double getScore3() {
        return score3;
    }

    public void setScore3(double score3) {
        this.score3 = score3;
    }
}