實驗二 Java類編程實驗

第1關 撰寫一個代表三角形的類

package step1;

import java.util.Scanner;

public class Triangle {
	// 自行設計類的實作
	/********** 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; //定義三條邊
		a = sc.nextDouble();
		b = sc.nextDouble();
		c = sc.nextDouble();
		Triangle t1 = new Triangle(a, b, c);
		//輸出面積
		System.out.println(t1 + "的面積為:" + String.format("%.2f", t1.getArea()));
		//輸出周長
		System.out.println(t1 + "的周長為:" +  String.format("%.2f", t1.getPerimeter()));	
		/********** End **********/
	}
}

第2關 撰寫一個圓環類

package step2;

public class Ring {
	/********** Begin **********/
	//自行設計類的實作  
	  private double innerRadius; //內半徑
    private double outerRadius; //外半徑
    private String color; //顏色

    //構造方法
    public Ring(double innerRadius, double outerRadius, String color){
        this.innerRadius = innerRadius;
        this.outerRadius = outerRadius;
        this.color = color;
    }

    //計算圓環面積
    public double area() {
        return Math.PI * (outerRadius * outerRadius - innerRadius * innerRadius);
    }

    //計算圓環外圓周長
    public double perimeter() {
        return 2 * Math.PI * outerRadius;
    }

    //計算圓環內圓周長
    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("圓環的內半徑: %.1f\n", ring.getInnerRadius());
		System.out.printf("圓環的外半徑: %.1f\n", ring.getOuterRadius());
		System.out.println("圓環的顏色: " + ring.getColor());
		System.out.printf("圓環的面積: %.2f\n", ring.area());
		System.out.printf("圓環的外圓周長: %.2f\n", ring.perimeter());
		System.out.printf("圓環的內圓周長: %.2f\n", ring.innerPerimeter());
		System.out.println();

		ring.setInnerRadius(4);
		ring.setOuterRadius(6);
		ring.setColor("blue");

		System.out.printf("圓環的內半徑: %.1f\n", ring.getInnerRadius());
		System.out.printf("圓環的外半徑: %.1f\n", ring.getOuterRadius());
		System.out.println("圓環的顏色: " + ring.getColor());
		System.out.printf("圓環的面積: %.2f\n", ring.area());
		System.out.printf("圓環的外圓周長: %.2f\n", ring.perimeter());
		System.out.printf("圓環的內圓周長: %.2f\n", ring.innerPerimeter());
	}
}

第3關 撰寫一個學生類

package step3;

public class Student {
	/********** Begin **********/
	// 自行設計類的實作
    // 成員變數
    private int id;     // 學號
    private int age;    // 年齡
    private String name;    // 姓名

    // 構造方法
    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，回傳學生的字串表示
    public String toString() {
        return "學號:" + id + ",姓名:" + name + ",年齡:" + age;
    }
	/********** End **********/
                                                     
	public static void main(String args[]) {
		Student s1 = new Student(1, 18, "小明");
		Student s2 = new Student(2, 20, "小張");
		Student s3 = new Student(3, 19, "小李");
		Student s4 = new Student(4, 18, "小王");
		Student s5 = new Student(5, 20, "小趙");

		Student s[] = { s1, s2, s3, s4, s5 }; // 給物件陣列賦值
		System.out.println("班級學生名單如下：");
		output(s); // 第1次呼叫output方法輸出陣列
		/********** Begin **********/
		// 將所有學生年齡加 1
        for (int i = 0; i < s.length; i++) {
            s[i].age++;
        }
		/********** End **********/                             
		System.out.println("所有學生年齡加 1 后...");
		output(s); /// 第2次呼叫output方法輸出陣列
		int count = 0;
		/********** Begin **********/
		//統計大于20歲的學生個數
        for (int i = 0; i < s.length; i++) {
            if (s[i].age > 20) {
                count++;
            }
        }
		/********** End **********/                    
		System.out.println("大于 20 歲人數是：" + count);
	}

	/* 以下方法輸岀學生陣列的所有元素 */
	private static void output(Student s[]) {
		for (int i = 0; i < s.length; i++)
			System.out.println(s[i]);
	}
}

標籤：Java

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