老人家的舊書房

import java.io.*;

public class ex5_5{
public static void main(String[] alio)
throws IOException{

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("請輸入欲計算之面積形狀：");
System.out.println("1.三角形。2.梯形。3.矩形。");
System.out.print("→");
String str = br.readLine();
int i = Integer.parseInt(str);

switch(i){
case 1:
System.out.println("請輸入底：");
String str2 = br.readLine();
int j = Integer.parseInt(str2);
System.out.println("請輸入高：");
String str3 = br.readLine();
int k = Integer.parseInt(str3);
int l = j * k / 2;
System.out.println("三角形面積為" + l);
break;
case 2:
System.out.println("請輸入上底：");
String str4 = br.readLine();
int jj = Integer.parseInt(str4);
System.out.println("請輸入下底：");
String str5 = br.readLine();
int kk = Integer.parseInt(str5);
System.out.println("請輸入高：");
String str6 = br.readLine();
int ll = Integer.parseInt(str6);
int f = (jj+kk)*ll/2;
System.out.println("梯形面積為" + f);
break;
case 3:
System.out.println("請輸入長：");
String str7 = br.readLine();
int jjj = Integer.parseInt(str7);
System.out.println("請輸入寬：");
String str8 = br.readLine();
int kkk = Integer.parseInt(str8);
int ly = jjj*kkk;
System.out.println("矩形面積為"+ ly);
break;
default:
System.out.println("輸入格式錯誤，程式即將關閉") ;
}

}
}