Printing out a Random Array

[BigDaddyLH]

Why not use java.util.Array s? You're importing it:
[CODE=java]import java.util.Array s;

public class Compact {
public static void main(String[] args) {
int a[] = new int[20];
for (int i = 0; i < a.length ; i++) {
a[i] = (int)(Math.rand om() * 10);
}
System.out.prin tln("The random array is: "
+ Arrays.toString (a));
}
}[/CODE]

The reason you were not getting the right output before is because the toString method for arrays doesn't output their contents.

[Laharl]

Your code as it is will print out the memory address of the array, not the actual elements. The identifier on an array, when passed to System.out.prin tln() does not work like the identifier for a primitive type, such as an integer. Instead, it prints out the memory location.

[CODE=java]
System.out.prin tln(a); //Only prints a's address, since a is actually a pointer to the array

for (int b = 0; b < a.length; b++) //Prints out each address on one line, then a newline
System.out.prin t(a[b]+" ");
System.out.prin tln(); //Newline
[/CODE]

[Energizer100]

Your code as it is will print out the memory address of the array, not the actual elements. The identifier on an array, when passed to System.out.prin tln() does not work like the identifier for a primitive type, such as an integer. Instead, it prints out the memory location.

[CODE=java]
System.out.prin tln(a); //Only prints a's address, since a is actually a pointer to the array

for (int b = 0; b < a.length; b++) //Prints out each address on one line, then a newline
System.out.prin t(a[b]+" ");
System.out.prin tln(); //Newline
[/CODE]

I got it working, thanks

[Energizer100]

I got it working, thanks

Okay, now that that is done. I have another problem.

I want to get rid of all of the zeroes in the random array. For example, the output would look something like this.

1 0 2 3 4 5 6 7 8 0 9 9 8 7 6 5 4 3 2 1 //Prints out the initial random array
1 2 3 4 5 6 7 8 9 9 8 7 6 5 4 3 2 1 //Prints out the same array but without the zeroes.


So here is my idea

import java.util.Arrays;

public class Compact 
{
	public static void main(String args[])
	{	
		int a[] = new int[20];	

		for (int i = 0; i < a.length; i++)
			{
				int b = (int) (Math.random() * 10);
				a[i] = b;
				System.out.print(a[i] + " ");
			}
		
		for (int k = 0; k < a.length; k++)
			{
				if (a[k] == 0)
				{
					//remove a zero
					int temp = a[k];
				}
			}	
	}
}

So what I am trying to do is store all the zeroes in temp, then when i print out the random array without the zeroes, i'll just subtract temp from it.

[Laharl]

There's a simpler way to do this. Simply use an if statement, saying if a[i]!=0, execute the printing code. That way, all the nonzero elements get printed, without any annoying removal code. If you really want to do that, I'd recommend an ArrayList.

[Energizer100]

There's a simpler way to do this. Simply use an if statement, saying if a[i]!=0, execute the printing code. That way, all the nonzero elements get printed, without any annoying removal code. If you really want to do that, I'd recommend an ArrayList.

It's an assignment, and I'm not allowed to use ArrayList

[Laharl]

Selective printing (the if statement) is by far the easiest solution. If you actually have to remove the zeroes, this problem is far more difficult.

[Energizer100]

Selective printing (the if statement) is by far the easiest solution. If you actually have to remove the zeroes, this problem is far more difficult.

I have to remove the zeros

[Laharl]

Given that arrays cannot be resized, you'll need a new array composed of the nonzero elements of the original. If you're limited to one array, you can push the zeroes to either end, then print either starting from the first nonzero or ending at the last end.

[Energizer100]

Given that arrays cannot be resized, you'll need a new array composed of the nonzero elements of the original. If you're limited to one array, you can push the zeroes to either end, then print either starting from the first nonzero or ending at the last end.

oh. So i just move the zeroes to the end and print out the first non zero integer all the way to the last non zero integer? How do I do that? I was thinking about using a for loop and adding it to the last one. So when the for loop hits the last integer, all the zeros would go to the end.

[Laharl]

Kind of. When you find the first zero, you want to switch it with the last element. The second, the second to last element. And so on. To do this, you can keep track of how many you've found and access the appropriate element near the end to switch with (length-count, make sure you increment count at the right time). Note that if the element you're trying to switch with is a zero, you have to move to the next element towards the front until you have a nonzero to switch with.

[Energizer100]

Kind of. When you find the first zero, you want to switch it with the last element. The second, the second to last element. And so on. To do this, you can keep track of how many you've found and access the appropriate element near the end to switch with (length-count, make sure you increment count at the right time). Note that if the element you're trying to switch with is a zero, you have to move to the next element towards the front until you have a nonzero to switch with.

wouldn't that just switch the array around?

for example

1 0 0 2 3 4 5 6 7 8 0 9 2 1 4 6 0 4 // regular array
1 4 0 2 3 4 5 6 7 8 6 9 2 1 4

[JosAH]

If you don't want zeros in your array, I'd say don't put them in there in the first place.

kind regards,

Jos

[Energizer100]

If you don't want zeros in your array, I'd say don't put them in there in the first place.

kind regards,

Jos

well, its kind of an assignment. First I have to print out the random array, then i print out that array without zeros

[JosAH]

well, its kind of an assignment. First I have to print out the random array, then i print out that array without zeros

Simply iterate (loop) over the array; if you see a non-zero number then print it,
otherwise skip it (i.e. do nothing).

kind regards,

Jos