JAVA作业）01

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一，四则运算

（一）  设计思想

使用Scanner类读取运行时用户输入数据，然后进行数据类型转换，完成四则运算之后利用输出类输出。

（二）  流程图

（三）程序代码

//Zhangxiaochen 2015/10 04  四则运算

import javax.swing.JOptionPane;  // import class JOptionPane

public class Operation {

         public static void main( String args[] )

            {

               String firstNumber,   // first string entered by user

                      secondNumber;  // second string entered by user

               int number1,          // first number to add

                   number2,          // second number to add

                   sum,             // sum of number1 and number2

                     redu,                              //reduction of number1 and number2

                     pro;                                //product of  number1 and number2

               float div;                                //divistor of number1 and number2

               // read in first number from user as a string

               firstNumber =

                  JOptionPane.showInputDialog( "Enter first integer" );

               // read in second number from user as a string

               secondNumber =

                  JOptionPane.showInputDialog( "Enter second integer" );

               // convert numbers from type String to type int

               number1 = Integer.parseInt( firstNumber );

               number2 = Integer.parseInt( secondNumber );

               // add the numbers

               sum = number1 + number2;

               redu=number1 - number2;

               pro=number1 * number2;

               div=number1 /number2;

               // display the results

               JOptionPane.showMessageDialog(

                  null,

                  "和是：" + sum+"\n"+

                  "差是：" + redu+"\n"+

                  "积是：" + pro+"\n"+

                  "商是：" + div+"\n",

                  "Results",

                  JOptionPane.PLAIN_MESSAGE );

               System.exit( 0 );   // terminate the program

            }

}

（四）运行截图

二EnumTest

（一）  程序代码

public class EnumTest {

         public static void main(String[] args) {

                  Size s=Size.SMALL;

                  Size t=Size.LARGE;

                  //s和t引用同一个对象？

                  System.out.println(s==t);  //

                  //是原始数据类型吗？

                  System.out.println(s.getClass().isPrimitive());

                  //从字符串中转换

                  Size u=Size.valueOf("SMALL");

                  System.out.println(s==u);  //true

                  //列出它的所有值

                  for(Size value:Size.values()){

                          System.out.println(value);

                  }

         }

}

enum Size{SMALL,MEDIUM,LARGE};

（二）  运行截图

（三）  思考

枚举类型不能直接运算，需要进行类型转换才能比较大小或运算。

三TestDouble

（一）  程序代码

public class TestDouble {

    public static void main(String args[]) {

        System.out.println("0.05 + 0.01 = " + (0.05 + 0.01));

        System.out.println("1.0 - 0.42 = " + (1.0 - 0.42));

        System.out.println("4.015 * 100 = " + (4.015 * 100));

        System.out.println("123.3 / 100 = " + (123.3 / 100));

    }

}

（二）运行截图

（三）思考

double类型由于精度问题会产生数据精度损失

JAVA作业）01

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原文地址：http://www.cnblogs.com/420Rock/p/4860055.html