loop problem

[ming ming]

   
public class FishClass {
     int numberOfFish=0;
    private int fishAmount=2;
    Fish [] fish=new Fish[fishAmount];
    public void setFish(String name,int age){   
    for(;numberOfFish<=fishAmount;numberOfFish++){   
        fish[numberOfFish]=new Fish();
    fish[numberOfFish].setName(name);
        fish[numberOfFish].setAge(age);  
       // numberOfFish++;       
    }
    }
   public Fish getFish(int x){
   return fish[x];
   }
}
 
 

In the above code why can't i use the for loop to add in data??

[Keith Lynn]

What error do you get?

[marc weber]

Remember, array indexing starts at zero. So if the array size is "fishAmount," then an index equal to fishAmount will be out of bounds...

numberOfFish<=fishAmount

[ming ming]

the error i get is indexoutofbound.....
so,where should i modify in my code???

[marc weber]

Originally posted by ming ming:
the error i get is indexoutofbound.....
so,where should i modify in my code???

You're out of bounds when the index equals fishAmount. So instead of less than or equal to fishAmount, you just want less than fishAmount...

...numberOfFish <= fishAmount; ...
                 ^
                 Out of bounds when equal

[ming ming]

it still can't work...stil the same error....
i'm doing things like set the size of the array is 2 then when i add more it will automatic increase the size of it...

[Keith Lynn]

It is easier if you use the length field of the array in the condition rather than a number you will have to change.

You can't change the size of an array once it's created. However, you can create another array whose size is larger than the first, copy the contents of the first into the array, and then change the original reference to point to the new array.
[ May 27, 2006: Message edited by: Keith Lynn ]

[marc weber]

Originally posted by ming ming:
...i'm doing things like set the size of the array is 2 then when i add more it will automatic increase the size of it...

That's the behavior of an ArrayList -- not an array. As Keith pointed out, you can't change the size of an array once it's instantiated.

[ming ming]

now i have change to use arraylist, but i still not sure why i can't use it..

 
package firstPackage;
import java.util.ArrayList;
 
public class FishClass {
     int numberOfFish=0;
    protected static int fishAmount=2;
    Fish [] fish=new Fish[fishAmount]; //Once set cannot be changed anymore.
    public void setFish(String name,int age){   
    ArrayList list=new ArrayList(fishAmount);
    for(;numberOfFish<fish.length;numberOfFish++){
    list.add(fish[numberOfFish].setName(name)); //is it something wrong here?
    }
    }
   public Fish getFish(int x){
   return fish[x];
   }
}
  
 

[wise owen]

class FishClass {

    private List lstFish = new ArrayList();
 
    public void setFish(String name,int age, int numberOfFish) {
    while (numberOfFish-- >0) {
        Fish f = new Fish();
        f.setName(name);
        f.setAge(age);
        lstFish.add(f);
    }
    }
    public int size() {
    return lstFish.size();
    }
 
    public Fish getFish(int x) {
   if (x >=0 && x< lstFish.size())
        return (Fish)lstFish.get(x);
   else
        return null;
   }
 }

[ming ming]

i do not want to use arraylist because of some reason, i have succesfully resize it but now i can't access the data inside it, when i tried to use getName it will show NullPointerException..What happened? i dun see any object is null
Mayb someone can point it out 4 me..

  
package firstPackage;
 
public class FishClass {
 
    int numberOfFish=0;
    protected int fishAmount=2;
    Fish[] fish=new Fish[fishAmount];
    int y=0;
  
    public void setFish1(String name,int age){ 
          y++;   //This will check how many data is the array should have
          setSize();
          setFish2(name,age);  
    } 
    public void setSize(){
    fish=new Fish[y];
    }
    public void setFish2(String name,int age){
          fish[numberOfFish]=new Fish();
          fish[numberOfFish].setName(name);
          fish[numberOfFish].setAge(age);
          numberOfFish++;  
    }
    public Fish getFish(int x){
   return fish[x];
    } 
}
 

 
package firstPackage;
 
public class TestFish {

public static void main(String[] args) {

         FishClass tes=new FishClass();
         
         tes.setFish1("Kok",18);
         tes.setFish1("Ming",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Ming",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Ming",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Ming",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Ming",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Ming",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Ming",18);
         tes.setFish1("Kok",18);
         tes.setFish1("Ming",18);
         tes.setFish1("Kok",18);
        
         for(int x=0;x<tes.y;x++){   
         System.out.println(tes.getFish(x).getName()); //Only when i tried
                                                            //to access here.
                                                            //Error came in.
         }
         
}
}
 
  

[wise owen]

public void setFish1(String name,int age){
y++;
setSize();
setFish2(name,age);
}
public void setSize(){
fish=new Fish[y];
}

You redefine the Fish array every time. In the end, you only keep one Fish instance in your new array (the last one in your array).

[ming ming]

how can i solve that if i put fish=new Fish[y]; this into instance variable it doesn't allow me to do it...any better solution for this?