JAVA作业）01

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