Java: sort parallel arrays - Overclock.net

Nuxes · 05-08-08

For my Java final project, I have to create a program that will allow a user to sort and search through a list of CDs:

I have put them into two 2-dim arrays:

Code:

String[][] first = { {"AC/DC", "Plug me In"},
                         {"Beatles", "Yellow Submarine"},
                         {"Creed", "Human Sacrifice"},
                         {"U-2", "The Joshua Tree"},
                         {"Queen", "Say It's Not True"},
                         {"Eric Clapton", "Rush"},
                         {"MatchBox 20", "Bent"},
                         {"Aero Smith", "Just Push Play"},
                         {"Chris Isaak", "Best of Chris Isaak"},
                         {"U-2", "Window in the Skies"},
                         {"Elton John", "Rocketman"},
                         {"Tool", "The Lowdown"}
                         {"Queen", "Another One Bites the Dust"},
                         {"MatchBox 20", "Matchbox 20"},
                         {"Foo Fighters", "The Pretender"}
                         {"Eric Clapton", "Tears in Heaven"};
                       }
                       
int[][] second = {{101,2},
    		      {2, 5},
                      {56, 23},
                      {60, 23},
                      {34, 7},
                      {5, 26},
                      {15, 9},
                      {42, 12},
                      {31, 11},
                      {60, 24},
                      {18, 18},
                      {13, 1}
                      {24, 8},
                      {15, 6},
                      {16, 19}
                      {22, 20};
    				 }

My problem is, how do I sort one (by artist name, bin number, etc.) array and keep the other in sync? Also, I would probably be easiest to put this in a single method, but how would I tell it how to sort?

legoman786 · 05-08-08

Use the [code] tags if you want to keep everything in order on the forums

I'd help you but I don't know jack about Java.

Nuxes · 05-08-08

Quote:

Originally Posted by legoman786

Use the [code] tags if you want to keep everything in order on the forums

I'd help you but I don't know jack about Java.

Ah, thank you!

Manyak · 05-08-08

Check out these sorting algorithms.

The easiest one is called bubblesort. And all you need to do is use the same indexes between both arrays.

it goes something like:

Code:

var i;
var j;

for (i=0; i<array.length; i++)
    for (j=array.length; j>i+1; j--)
        if (array[j-1][0] > array[j][0])
        {
            swap(array[j-1], array[j]);
            swap(second_array[j-1], second_array[j]);
        }

Nuxes · 05-08-08

So would this be correct for sorting by bin number?

Code:

private static void sortarray(int[][] array){
	   
	int i,j;

	for (i=0; i<array.length; i++)
    	    for (j=array.length; j>i+1; j--)
        	if (second[0][j-1] > first[0][j])
        	{	
                 swap(second[j-1], second[j]);
                 swap(first[j-1], first[j]);
        	}
	}

rabidgnome229 · 05-08-08

Instead of using 2 2D arrays you should use 4 1D arrays. The way it is coded now would make the code a bit more complicated, and storing in an nx2 matrix rather than a 2xn matrix can decrease performance by up to half.

The cleanest way to implement this is with a class for entries

Code:

public class CDEntry implements Comparable{
	public String artist, title;
	int code, bin;
	
	public CDEntry(String a, String t, int c, int b){
		artist = a; title = b;
		code = c; bin = b;
	}
	
	public CDEntry(){
		artist = title = null;
		code = bin = 0;
	}
	
	int compareTo(Object o){
		if(! (o instanceof CDEntry))
			return 1;
		CDEntry other = (CDEntry)o;
		if(other.bin > bin) return -1;
		else if(other.bin == bin) return 0;
		else return 1;
	}
}

Then you can create a single array of entries. Making it implement Comparable allows you to use the Arrays.sort(Object[] o) method to sort it using an optimized algorithm that you don't have to write yourself

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Java: sort parallel arrays

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