9.15代码试验

Addition.java

package shiyan;


// 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
    }
}

EnumTest.java

package shiyan;

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};

InputTest.java

package shiyan;

/**
 @version 1.10 2004-02-10
 @author Cay Horstmann
 */

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));


    }
}

RandomStr.java

package shiyan;




public class RandomStr
{
    public static void main(String[] args)
    {
        //定义一个空字符串
        String result = "";
        //进行6次循环
        for(int i = 0 ; i < 6 ; i ++)
        {
            //生成一个97～122的int型的整数
            int intVal = (int)(Math.random() * 26 + 97);
            //将intValue强制转换为char后连接到result后面
            result = result + (char)intVal;
        }
        //输出随机字符串
        System.out.println(result);
    }
}

SwitchTest.java

package shiyan;

// Drawing shapes
import java.awt.Graphics;
import javax.swing.*;

public class SwitchTest extends JApplet {
    int choice;

    public void init()
    {
        String input;

        input = JOptionPane.showInputDialog(
                "Enter 1 to draw lines\n" +
                        "Enter 2 to draw rectangles\n" +
                        "Enter 3 to draw ovals\n" );

        choice = Integer.parseInt( input );
    }

    public void paint( Graphics g )
    {
        for ( int i = 0; i < 10; i++ ) {
            switch( choice ) {
                case 1:
                    g.drawLine( 10, 10, 250, 10 + i * 10 );
                    break;
                case 2:
                    g.drawRect( 10 + i * 10, 10 + i * 10,
                            50 + i * 10, 50 + i * 10 );
                    break;
                case 3:
                    g.drawOval( 10 + i * 10, 10 + i * 10,
                            50 + i * 10, 50 + i * 10 );
                    break;
                default:
                    JOptionPane.showMessageDialog(
                            null, "Invalid value entered" );
            } // end switch
        } // end for
    } // end paint()
} // end class SwitchTest

Test.java

package shiyan;

public class Test {
    public static void main(String[] args) {
        int intValue=100;
        long longValue=intValue;
        double doubleValue=1234567890;
        float floatValue=(float)doubleValue;
        System.out.println(floatValue);//1.23456794E9

        int X=100;
        int Y=200;
        System.out.println("X+Y="+X+Y);
        System.out.println(X+Y+"=X+Y");
        doNotRunme();

        String string="";
        double d1=1000.123;
        double d2=1000.123;
        if(Math.abs(d2-d1)<1e-10){

        }
        //System.out.println(string);

    }

    public static void doNotRunme()
    {
        doNotRunme();
    }
}

TestBigDecimal.java

 

package shiyan;


import java.math.BigDecimal;

public class TestBigDecimal
{
    public static void main(String[] args)
    {
        BigDecimal f1 = new BigDecimal("0.05");
        BigDecimal f2 = BigDecimal.valueOf(0.01);
        BigDecimal f3 = new BigDecimal(0.05);
        System.out.println("下面使用String作为BigDecimal构造器参数的计算结果：");
        System.out.println("0.05 + 0.01 = " + f1.add(f2));
        System.out.println("0.05 - 0.01 = " + f1.subtract(f2));
        System.out.println("0.05 * 0.01 = " + f1.multiply(f2));
        System.out.println("0.05 / 0.01 = " + f1.divide(f2));
        System.out.println("下面使用double作为BigDecimal构造器参数的计算结果：");
        System.out.println("0.05 + 0.01 = " + f3.add(f2));
        System.out.println("0.05 - 0.01 = " + f3.subtract(f2));
        System.out.println("0.05 * 0.01 = " + f3.multiply(f2));
        System.out.println("0.05 / 0.01 = " + f3.divide(f2));
    }
}

TestDouble.java

package shiyan;



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));
    }
}