how to sort a multidimensional array

You will use the same Arrays.sort() method passing in your multi-dimensional array and a second Comparator parameter which specifies your ordering requirements. For example:

import java.util.*;

public class MultiSort

{

public static void main(String args[])

{

String[][] names = {

{"Smith","John"},

{"Smith","Albert"},

{"Jones","Sonny"},

{"Jones","Sam"},

};

System.out.println("Before sort...");

printArray(names);

System.out.println();

Arrays.sort(names,new LastFirstComparator());

System.out.println("After sort...");

printArray(names);

}

public static void printArray(String[][] array)

{

for (int i = 0; i < array.length; i++)

{

for (int j = 0; j < array[i].length; j++)

{

System.out.print(array[i][j]);

System.out.print("\t");

}

System.out.println();

}

}

}

class LastFirstComparator implements Comparator

{

public int compare(Object obj1, Object obj2)

{

int result = 0;

String[] str1 = (String[]) obj1;

String[] str2 = (String[]) obj2;

/* Sort on first element of each array (last name) */

if ((result = str1[0].compareTo(str2[0])) == 0)

{

/* If same last name, sort on second element (first name) */

result = str1[1].compareTo(str2[1]);

}

return result;

}

}

paternostroa at 2007-7-15 22:39:22 >

I copied and tried to compile this example and am getting an error I don't understand. I'm pretty new to Java programming; any help would be appreciated.

The error is:

MultiSort.java:20: warning: [unchecked] unchecked conversion

found: LastFirstComparator

required: java.util.Comparator<? super java.lang.String[]>

Arrays.sort(names,new LastFirstComparator());

^

MultiSort.java:20: warning: [unchecked] unchecked method invocation: <T>sort(T[]

,java.util.Comparator<? super T>) in java.util.Arrays is applied to (java.lang.S

tring[][],LastFirstComparator)

Arrays.sort(names,new LastFirstComparator());

Tostiga at 2007-7-15 22:39:22 >