Posts by tong1

In the following method, why the factorial goes wrong when n>12 ? */

static int factorial(int n){
		int fac=1;
		if ((n<0) || (n>12))
		return -1;
		for (int i=2; i<=n;i++)
		fac *=i;
		return fac;
	}

/* Operation on DOS window: "PositiveInt1" receives a positive integer only.  */
import java.util.*;
public class PositiveInt1{
	
    public static void main(String args[]){
    	int n=0;
    	Scanner in = new Scanner(System.in);
    	
   	while(true){
	try{
System.out.println("Input a non-negative integer:");
	n = in.nextInt();
   	}catch(InputMismatchException e){
	System.out.println("Your input is mismatched.");
	in.next();
 	continue;
  	}
  	if (n<0){
  	System.out.println("You negative value is not valid.");
  	continue;
  	}
       	break;
    }
	
    System.out.printf("Your input is %d\n", n);
	}
}

/* “PositiveInt.java” receives an integer greater than 0. In this program Exceptions are catched accordingly */
import javax.swing.*;
public class PositiveInt{
	static class NonNegativeException extends Exception{
	public NonNegativeException(String msg){
		super(msg);
	}	
	}
	static void show(int x)throws NonNegativeException {
		if (x<0)
		throw new NonNegativeException("Negative integer is not valid.");
	}
    public static void main(String args[]){
    	int n=0;
	while(true){
		try{
		String s=JOptionPane.showInputDialog(null,"Input a positive integer:");
    	n = Integer.parseInt(s);
    	show(n);
    	}catch(NumberFormatException e){
    	System.out.println();
    	JOptionPane.showMessageDialog( null, "Your input is mismatched. Try again.", "Warning ",JOptionPane.WARNING_MESSAGE);
    	continue;
    	}catch(NonNegativeException e){
    	JOptionPane.showMessageDialog( null, e.getMessage(), "Warning ",JOptionPane.WARNING_MESSAGE);
    	continue;	
    	}
    	 break;    
    }
    JOptionPane.showMessageDialog(null,"Your input: "+n,"Welcome to DANIWEB", JOptionPane.INFORMATION_MESSAGE);
    }
}

/*The rocks are classified into the following 3 groups in origin:
Sedimentary, Igneous, and Metaphorphic. */
class Rock{
    private double weight;
    private static int total=0;
    private String origin;

    public Rock(double w, String s){
        setWeight(w);
        System.out.println("Rock " + ++total + " is created");
        origin = s;
    }

    public void roll(){
        weight *=1.2;
    }

    public void setWeight(double d){   //成员方法
        weight = d>0?d:1;
    }
    public double getWeight( ){
        return weight;
    }
    public String getOrigin(){
        return origin;
    }
}

public class RockTest{
    public static void main(String args[]){
        String s[]={"Sedimentary","Igneous","Metamorphic"};
    Rock rock[]= new Rock[3];
    for (int i=0; i<3; i++)
    rock[i]=new Rock(10,s[i]);
    rock[1].roll();
    System.out.println("The " + rock[1].getOrigin() + " rock 2 has " + rock[1].getWeight() + " kg in weight after rolling.");

    }
}

class Rock{
    double weight;
    static int total=0;

    public Rock(double w){
        setWeight(w);
        System.out.println("Rock " + ++total + " is created");
    }

    void roll(){
        weight *=1.2;
    }

    void setWeight(double d){   //成员方法
        weight = d>0?d:1;
    }
    double getWeight( ){
        return weight;
    }
}

public class RockTest{
    public static void main(String args[]){
    Rock rock[]= new Rock[3];
    for (int i=0; i<3; i++)
    rock[i]=new Rock(10);
    rock[1].roll();
    System.out.println("The rock 2 has " + rock[1].getWeight() + " kg in weight after rolling.");

    }
}

// I have corrected your program as follows:
import javax.swing.*; 
public class speedofsound {
public static void main(String[] args) {
    String input;
    int medium = 0; 
medium = Integer.parseInt(  JOptionPane.showInputDialog(null, "Enter 1, 2 or 3 \nPick a medium : 1 for Air, 2 for Water and 3 for Steel")); 

switch (medium) {

    case 1:
        System.out.println ( " You have chosen Air" ); break;

    case 2:
        System.out.println ( " You have chosen Water");break;

    case 3:
        System.out.println (" You have chosen Steel");break;

    default:
        System.out.println ("Invalid choice");
        }
        }

}

Is your JLabel's instance on a background painted by the Graphics in AWT?
If the background is made by the Graphics's object, there will be a trouble. The stuff in AWT is considered as heavyweighted while the stuff, such as JLabel's instance in swing, lightweighted. The heaveweighted stuff always "overwrites" the lightweighted one.
Solution:
Use Label in AWT rather than JLabe in swing.

import java.util.*;

class cat{
	String name;
	int age;
	double weight;
	String breed;
	boolean declawed;
	public cat(String s, int n, double d, String bs, boolean dec){
		age=n;
		name = s;
		weight = d;
		breed = bs;
		declawed = dec;
	}
public	String getName(){
	return name;
} 	
public int getAge(){
	return age;
}
}
public class OwensDianaWeek6Prog
{
    public static void main (String[] args)
    {
       cat MyCat[] = new cat[3];


       Scanner input = new Scanner(System.in);
       for (int i=0; i<3; i++)
       {
          System.out.println("Enter the name of cat" + (i+1) + ":");
          String name = input.next();
          System.out.println("Enter the age of cat" + (i+1) + ":");
          int age = input.nextInt();
          System.out.println("Enter the weight of cat" + (i+1) + ":");
          double weight = input.nextDouble();
          System.out.println("Enter the breed of cat" + (i+1) + ":");
          String breed = input.next();
          System.out.println("Is cat" + (i+1) +  "declawed? True or False:");
          boolean declawed = input.nextBoolean();
          MyCat[i] = new cat(name, age, weight,breed,declawed);
          }
          
		  System.out.println("The cats over 3 with claws are:");	
		for (int i=0; i<3; i++)
       if ((MyCat[i].age >= 3) && (MyCat[i].declawed == false)){
		     System.out.println("Name: " + MyCat[i].getName());
		     System.out.println("Age: " + MyCat[i].getAge() + "Years Old");
       } //end if

    } // main
} // end class OwensDianaWeek6Prog