1.編寫一個圓類Circle,該類擁有：...，並列印輸出

package test;

public class Circle {
	
	protected  double radius;
	
	public Circle(){
		radius = 0;
	}
	public Circle(double r){
		radius =  r ;
	}
	
	public  double getArea() {
		return radius*radius*Math.PI;
	}
	
	public double getPerimeter() {
		return 2*Math.PI*radius;
	}
	
	public void show() {
		System.out.println("圓的半徑 ："+radius);
		System.out.println("圓的周長 ："+getPerimeter());
		System.out.println("圓的面積 ："+getArea());
	}
	
	
	public static void main (String args[]) {
		
		Cylinder c = new Cylinder(2,3.0);
		c.show();
		//c.showVolume();
	}
	
}
 

2.編寫一個圓柱類Cylinder,它繼承於上面的Circle類。還擁有：...

package test;

public class Cylinder extends Circle {
	private double hight;
	
	public Cylinder (double r, double h) {
		super(r);
		this.hight = h;
		
	}
	
	public  double getVolume() {
		return super.getArea()*hight;
	}

	void showVolume() {
		System.out.println("圓柱的體積："+getVolume());
	}
}
 

3.求1~100能被三整除的個數是多少？並求和。

package test;

import java.awt.List;
import java.util.ArrayList;

public class DivisibleSum {
	private static ArrayList arr = new ArrayList();
	private static  int num=0;
	
	public static  void divisible(int x) {
		
		for (int i = 1;i<101;i++) {
			if(i%x==0) {
				//a[num]=i;
				arr.add(i);
				num++;	
			}
		}
	}
	
	public static void main (String args[]) {
		
		divisible(3);
		System.out.println("被3整除的個數"+num);
		
		int sum =0;
		for(int i = 0; i<arr.size();i++)
		{
			System.out.print(arr.get(i)+",");
			int s= (int) arr.get(i);
			sum += s;
		}
		System.out.println("1~100能被3整除的數求和："+sum);
		
	}
}
 

4.輸入一個字串，判斷是否為迴文？

package test;

import java.util.Scanner;

public class HuiwenTest {
	
	//輸入字串 reverse倒置，然後比較
	public static  void main (String agrs[]) {
		
		System.out.print("請輸入一個字串：");
		Scanner input = new Scanner(System.in);
		
		String str = input.next();
		StringBuffer buff = new StringBuffer(str);
		buff.reverse();
		String newstr = new String(buff);
		
		if(str.equals(newstr)) {
			System.out.println(str+" 此字串是迴文！");
		}else {
			System.out.println(str+" 字串不是迴文！");
		}
	}
}

5.氣泡排序（找出第二大的數）

package test;

public class BubbleSort {
	
	public static int[] bubbleSort(int arr[]) {
		
		for(int i = 0;i<arr.length-1;i++) {//冒泡趟數
			for(int j=0;j<arr.length-i-1;j++) {
				
				int temp ;
				if(arr[j]>arr[j+1]) {
					temp =arr[j];
					arr[j] = arr[j+1];
					arr[j+1] = temp;
				}
			}
		}
		return arr;
	}
	
	
	public static void main(String args[]) {
		int[] a = {3,26,1,4,7,29,9,7,63};
		a = bubbleSort(a);
		for(int i = 0; i<a.length;i++) {
			System.out.print(a[i]+",");
		}
		
		System.out.println("陣列中第二大的數是：" +a[a.length-2]);
	}

}

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