java课件运行实践

1. 两数相加   

源文件：Addition.java

源代码：

// An addition program

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

public class Addition {

   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

      // 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;

      // display the results

      JOptionPane.showMessageDialog(

         null, "The sum is " + sum, "Results",

         JOptionPane.PLAIN_MESSAGE );

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

   }

}

运行截图：

1. 枚举

源文件：EnumText.java

源代码：

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};

运行截图

1. 读取输入

源文件InputTest.java

源代码

import java.util.*;

public class InputTest

{  

   public static void main(String[] args)

   {  

      Scanner in = new Scanner(System.in);

      // get first input

      System.out.print("What is your name? ");

      String name = in.nextLine();

      // get second input

      System.out.print("How old are you? ");

      int age = in.nextInt();

      

      

    /* int i;

     String value="100";

     i=Integer.parseInt(value);

     i=200;

     String s=String.valueOf(i);*/

     

      // display output on console

      System.out.println("Hello, " + name + ". Next year, you'll be " + (age + 1));

  

      

   }

}

运行截图

4double类型.

源文件 TestDouble.java

源代码

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));

    }

}

运行截图