9.15代码试验

Addition.java

 1 package shiyan;
 2 
 3 
 4 // An addition program
 5 
 6 import javax.swing.JOptionPane;  // import class JOptionPane
 7 
 8 public class Addition {
 9     public static void main( String args[] )
10     {
11         String firstNumber,   // first string entered by user
12                 secondNumber;  // second string entered by user
13         int number1,          // first number to add
14                 number2,          // second number to add
15                 sum;              // sum of number1 and number2
16 
17         // read in first number from user as a string
18         firstNumber =
19                 JOptionPane.showInputDialog( "Enter first integer" );
20 
21         // read in second number from user as a string
22         secondNumber =
23                 JOptionPane.showInputDialog( "Enter second integer" );
24 
25         // convert numbers from type String to type int
26         number1 = Integer.parseInt( firstNumber );
27         number2 = Integer.parseInt( secondNumber );
28 
29         // add the numbers
30         sum = number1 + number2;
31 
32         // display the results
33         JOptionPane.showMessageDialog(
34                 null, "The sum is " + sum, "Results",
35                 JOptionPane.PLAIN_MESSAGE );
36 
37         System.exit( 0 );   // terminate the program
38     }
39 }

EnumTest.java

 1 package shiyan;
 2 
 3 public class EnumTest {
 4 
 5     public static void main(String[] args) {
 6         Size s=Size.SMALL;
 7         Size t=Size.LARGE;
 8         //s和t引用同一个对象？
 9         System.out.println(s==t);  //
10         //是原始数据类型吗？
11         System.out.println(s.getClass().isPrimitive());
12         //从字符串中转换
13         Size u=Size.valueOf("SMALL");
14         System.out.println(s==u);  //true
15         //列出它的所有值
16         for(Size value:Size.values()){
17             System.out.println(value);
18         }
19     }
20 
21 }
22 enum Size{SMALL,MEDIUM,LARGE};

InputTest.java

 1 package shiyan;
 2 
 3 /**
 4  @version 1.10 2004-02-10
 5  @author Cay Horstmann
 6  */
 7 
 8 import java.util.*;
 9 
10 public class InputTest
11 {
12     public static void main(String[] args)
13     {
14         Scanner in = new Scanner(System.in);
15 
16         // get first input
17         System.out.print("What is your name? ");
18         String name = in.nextLine();
19 
20         // get second input
21         System.out.print("How old are you? ");
22         int age = in.nextInt();
23 
24 
25     /* int i;
26      String value="100";
27      i=Integer.parseInt(value);
28      i=200;
29      String s=String.valueOf(i);*/
30 
31         // display output on console
32         System.out.println("Hello, " + name + ". Next year, you'll be " + (age + 1));
33 
34 
35     }
36 }

RandomStr.java

 1 package shiyan;
 2 
 3 
 4 
 5 
 6 public class RandomStr
 7 {
 8     public static void main(String[] args)
 9     {
10         //定义一个空字符串
11         String result = "";
12         //进行6次循环
13         for(int i = 0 ; i < 6 ; i ++)
14         {
15             //生成一个97～122的int型的整数
16             int intVal = (int)(Math.random() * 26 + 97);
17             //将intValue强制转换为char后连接到result后面
18             result = result + (char)intVal;
19         }
20         //输出随机字符串
21         System.out.println(result);
22     }
23 }

SwitchTest.java

 1 package shiyan;
 2 
 3 // Drawing shapes
 4 import java.awt.Graphics;
 5 import javax.swing.*;
 6 
 7 public class SwitchTest extends JApplet {
 8     int choice;
 9 
10     public void init()
11     {
12         String input;
13 
14         input = JOptionPane.showInputDialog(
15                 "Enter 1 to draw lines\n" +
16                         "Enter 2 to draw rectangles\n" +
17                         "Enter 3 to draw ovals\n" );
18 
19         choice = Integer.parseInt( input );
20     }
21 
22     public void paint( Graphics g )
23     {
24         for ( int i = 0; i < 10; i++ ) {
25             switch( choice ) {
26                 case 1:
27                     g.drawLine( 10, 10, 250, 10 + i * 10 );
28                     break;
29                 case 2:
30                     g.drawRect( 10 + i * 10, 10 + i * 10,
31                             50 + i * 10, 50 + i * 10 );
32                     break;
33                 case 3:
34                     g.drawOval( 10 + i * 10, 10 + i * 10,
35                             50 + i * 10, 50 + i * 10 );
36                     break;
37                 default:
38                     JOptionPane.showMessageDialog(
39                             null, "Invalid value entered" );
40             } // end switch
41         } // end for
42     } // end paint()
43 } // end class SwitchTest

Test.java

 1 package shiyan;
 2 
 3 public class Test {
 4     public static void main(String[] args) {
 5         int intValue=100;
 6         long longValue=intValue;
 7         double doubleValue=1234567890;
 8         float floatValue=(float)doubleValue;
 9         System.out.println(floatValue);//1.23456794E9
10 
11         int X=100;
12         int Y=200;
13         System.out.println("X+Y="+X+Y);
14         System.out.println(X+Y+"=X+Y");
15         doNotRunme();
16 
17         String string="";
18         double d1=1000.123;
19         double d2=1000.123;
20         if(Math.abs(d2-d1)<1e-10){
21 
22         }
23         //System.out.println(string);
24 
25     }
26 
27     public static void doNotRunme()
28     {
29         doNotRunme();
30     }
31 }

TestBigDecimal.java

 1 package shiyan;
 2 
 3 
 4 import java.math.BigDecimal;
 5 
 6 public class TestBigDecimal
 7 {
 8     public static void main(String[] args)
 9     {
10         BigDecimal f1 = new BigDecimal("0.05");
11         BigDecimal f2 = BigDecimal.valueOf(0.01);
12         BigDecimal f3 = new BigDecimal(0.05);
13         System.out.println("下面使用String作为BigDecimal构造器参数的计算结果：");
14         System.out.println("0.05 + 0.01 = " + f1.add(f2));
15         System.out.println("0.05 - 0.01 = " + f1.subtract(f2));
16         System.out.println("0.05 * 0.01 = " + f1.multiply(f2));
17         System.out.println("0.05 / 0.01 = " + f1.divide(f2));
18         System.out.println("下面使用double作为BigDecimal构造器参数的计算结果：");
19         System.out.println("0.05 + 0.01 = " + f3.add(f2));
20         System.out.println("0.05 - 0.01 = " + f3.subtract(f2));
21         System.out.println("0.05 * 0.01 = " + f3.multiply(f2));
22         System.out.println("0.05 / 0.01 = " + f3.divide(f2));
23     }
24 }

TestDouble.java

 1 package shiyan;
 2 
 3 
 4 
 5 public class TestDouble {
 6 
 7     public static void main(String args[]) {
 8         System.out.println("0.05 + 0.01 = " + (0.05 + 0.01));
 9         System.out.println("1.0 - 0.42 = " + (1.0 - 0.42));
10         System.out.println("4.015 * 100 = " + (4.015 * 100));
11         System.out.println("123.3 / 100 = " + (123.3 / 100));
12     }
13 }