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