实验二 Java类编程实验

第1关 编写一个代表三角形的类

package step1;import java.util.Scanner;public class Triangle {// 自行设计类的实现/********** Begin **********/    private double a;    private double b;    private double c;    public Triangle(double a, double b, double c) {        this.a = a;        this.b = b;        this.c = c;    }    public double getArea() {        double p = (a + b + c) / 2;        return Math.sqrt(p * (p - a) * (p - b) * (p - c));    }    public double getPerimeter() {        return a + b + c;    }    //@Override    public String toString() {        return String.format("三角形(%.1f,%.1f,%.1f)", a, b, c);    }/********** End **********/public static void main(String[] args) {/********** Begin **********/Scanner sc = new Scanner(System.in);double a,b,c; //定义三条边a = sc.nextDouble();b = sc.nextDouble();c = sc.nextDouble();Triangle t1 = new Triangle(a, b, c);//输出面积System.out.println(t1 + "的面积为:" + String.format("%.2f", t1.getArea()));//输出周长System.out.println(t1 + "的周长为:" +  String.format("%.2f", t1.getPerimeter()));/********** End **********/}}

第2关 编写一个圆环类

package step2;public class Ring {/********** Begin **********///自行设计类的实现    private double innerRadius; //内半径    private double outerRadius; //外半径    private String color; //颜色    //构造方法    public Ring(double innerRadius, double outerRadius, String color){        this.innerRadius = innerRadius;        this.outerRadius = outerRadius;        this.color = color;    }    //计算圆环面积    public double area() {        return Math.PI * (outerRadius * outerRadius - innerRadius * innerRadius);    }    //计算圆环外圆周长    public double perimeter() {        return 2 * Math.PI * outerRadius;    }    //计算圆环内圆周长    public double innerPerimeter() {        return 2 * Math.PI * innerRadius;    }    //getter和setter方法    public double getInnerRadius() {        return innerRadius;    }    public void setInnerRadius(double innerRadius) {        this.innerRadius = innerRadius;    }    public double getOuterRadius() {        return outerRadius;    }    public void setOuterRadius(double outerRadius) {        this.outerRadius = outerRadius;    }    public String getColor() {        return color;    }    public void setColor(String color) {        this.color = color;    }/********** End **********/                                                     public static void main(String[] args) {Ring ring = new Ring(5, 8, "red");System.out.printf("圆环的内半径: %.1f\n", ring.getInnerRadius());System.out.printf("圆环的外半径: %.1f\n", ring.getOuterRadius());System.out.println("圆环的颜色: " + ring.getColor());System.out.printf("圆环的面积: %.2f\n", ring.area());System.out.printf("圆环的外圆周长: %.2f\n", ring.perimeter());System.out.printf("圆环的内圆周长: %.2f\n", ring.innerPerimeter());System.out.println();ring.setInnerRadius(4);ring.setOuterRadius(6);ring.setColor("blue");System.out.printf("圆环的内半径: %.1f\n", ring.getInnerRadius());System.out.printf("圆环的外半径: %.1f\n", ring.getOuterRadius());System.out.println("圆环的颜色: " + ring.getColor());System.out.printf("圆环的面积: %.2f\n", ring.area());System.out.printf("圆环的外圆周长: %.2f\n", ring.perimeter());System.out.printf("圆环的内圆周长: %.2f\n", ring.innerPerimeter());}}

第3关 编写一个学生类

package step3;public class Student {/********** Begin **********/// 自行设计类的实现    // 成员变量    private int id;     // 学号    private int age;    // 年龄    private String name;    // 姓名    // 构造方法    public Student(int id, int age, String name) {        this.id = id;        this.age = age;        this.name = name;    }    // getter方法    public int getId() {        return id;    }    public int getAge() {        return age;    }    public String getName() {        return name;    }    // toString方法，返回学生的字符串表示    public String toString() {        return "学号:" + id + ",姓名:" + name + ",年龄:" + age;    }/********** End **********/                                                     public static void main(String args[]) {Student s1 = new Student(1, 18, "小明");Student s2 = new Student(2, 20, "小张");Student s3 = new Student(3, 19, "小李");Student s4 = new Student(4, 18, "小王");Student s5 = new Student(5, 20, "小赵");Student s[] = { s1, s2, s3, s4, s5 }; // 给对象数组赋值System.out.println("班级学生名单如下：");output(s); // 第1次调用output方法输出数组/********** Begin **********/// 将所有学生年龄加 1        for (int i = 0; i < s.length; i++) {            s[i].age++;        }/********** End **********/                             System.out.println("所有学生年龄加 1 后...");output(s); /// 第2次调用output方法输出数组int count = 0;/********** Begin **********///统计大于20岁的学生个数        for (int i = 0; i  20) {                count++;            }        }/********** End **********/                    System.out.println("大于 20 岁人数是：" + count);}/* 以下方法输岀学生数组的所有元素 */private static void output(Student s[]) {for (int i = 0; i < s.length; i++)System.out.println(s[i]);}}