switch case实现两个数的算术运算

方法一：

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package com.liaojianya.chapter1;   import java.util.Scanner;   public class SwitchDemo1 {     public static void main(String[] args)     {         Scanner input = new Scanner(System.in);         System.out.println("Enter number a : ");         double a = input.nextDouble();         System.out.println("Enter number b : ");         double b = input.nextDouble();         Action ac = new Action(a, b);         ac.command(Action.ADD);         ac.command(Action.SUBTRACT);         ac.command(Action.MULTIPLY);         ac.command(Action.DIVIDE);         ac.command(Action.MOD);         input.close();     } }   class Action {     double a;     double b;     public Action(double a, double b)     {         this.a = a;         this.b = b;     }     public static final int ADD = 1;     public static final int SUBTRACT = 2;     public static final int MULTIPLY = 3;     public static final int DIVIDE = 4;     public static final int MOD = 5;       public void command(int c)     {         switch (c)         {         case 1:             System.out.println(a + " + " + b + " = " + (a + b));             break;           case 2:             System.out.println(a + " - " + b + " = " + (a - b));             break;           case 3:             System.out.println(a + " * " + b + " = " + (a * b));             break;           case 4:             System.out.println(a + " / " + b + " = " + (a / b));             break;           case 5:             System.out.println(a + " % " + b + " = " + (a % b));             break;           default:             System.out.println("unknown operation!");             break;         }     }   }

　　方法二：

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package com.liaojianya.chapter1;   import java.util.Scanner;   /**  * This program demonstrates the use of switch.  * @author LIAO JIANYA  *  */ public class SwitchDemo {     public static void main(String[] args)     {         Scanner input = new Scanner(System.in);                   System.out.println("Enter number a : ");         double a = input.nextDouble();         System.out.println("Enter number b : ");         double b = input.nextDouble();         System.out.println("Enter  operater :1代表+，2代表-，3代表*，4代表/，5代表% ");         int c = input.nextInt();         switch(c)         {             case 1:             System.out.println(a + " + " + b + " = " + (a + b));             break;               case 2:             System.out.println(a + " - " + b + " = " + (a - b));             break;               case 3:             System.out.println(a + " * " + b + " = " + (a * b));             break;               case 4:             System.out.println(a + " / " + b + " = " + (a / b));             break;               case 5:             System.out.println(a + " % " + b + " = " + (a % b));             break;                           default:                 System.out.println("unknown operation!");                 break;         }     }   }

　　运行结果：

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Enter number a : 12.3 Enter number b : 32.1 12.3 + 32.1 = 44.400000000000006 12.3 - 32.1 = -19.8 12.3 * 32.1 = 394.83000000000004 12.3 / 32.1 = 0.38317757009345793 12.3 % 32.1 = 12.3