A friend asked me two days ago how to implement a sort algorithm on J2ME...
Never used the J2ME API but I thought, hey, can't be that bad right. I must say, after seeing the primitive nature of J2ME I don't think I would or even could do mobile dev. with that API. It'd drive me insane. In any case, I figured out a quick way of sorting an array of names in alphabetical order...<!-- more -->
J2ME has a RecordComparator interface defined as:
public interface RecordComparator {
public static final int PRECEDES = -1;
public static final int EQUIVALENT = 0;
public static final int FOLLOWS = 1;
public int compare(byte[] rec1, byte[] rec2);
}
Implement that interface in a class called RecordSorter
static class RecordSorter implements RecordComparator {
public int compare(byte[] rec1, byte[] rec2) {
String strRec1 = new String(rec1);
String strRec2 = new String(rec2);
return strRec1.compareTo(strRec2) == 0 ? EQUIVALENT
: (strRec1.compareTo(strRec2) > 0 ? FOLLOWS : PRECEDES);
}
}
Then you can use your class like this:
String data={"Melon","Grapes","Orange","Bananna"};
private void sortResults() {
RecordSorter sorter = new RecordSorter();
boolean changed = true;
while (changed) {
changed = false;
for (int j = 0; j < (data.length - 1); j++) {
String a = data[j], b = data[j + 1];
if (a != null && b != null) {
int order = sorter.compare(a.getBytes(), b.getBytes());
if (order == sorter.FOLLOWS) {
changed = true;
data[j] = b;
data[j + 1] = a;
}
}
}
}
}
In theory this will work in a normal Java app too...not tested though
UPDATE: As expected, it works in a normal Java app.
package sorting;
/**
*
* @author Courtney
*/
public class Sorting {
public interface RecordComparator {
public static final int PRECEDES = -1;
public static final int EQUIVALENT = 0;
public static final int FOLLOWS = 1;
public int compare(byte[] rec1, byte[] rec2);
}
static class RecordSorter implements RecordComparator {
public int compare(byte[] rec1, byte[] rec2) {
String strRec1 = new String(rec1);
String strRec2 = new String(rec2);
return strRec1.compareTo(strRec2) == 0 ? EQUIVALENT
: (strRec1.compareTo(strRec2) > 0 ? FOLLOWS : PRECEDES);
}
}
static String[] data = {"Melon", "Grapes", "Orange", "Bananna"};
private void sortResults() {
RecordSorter sorter = new RecordSorter();
boolean changed = true;
while (changed) {
changed = false;
for (int j = 0; j < (data.length - 1); j++) {
String a = data[j], b = data[j + 1];
if (a != null && b != null) {
int order = sorter.compare(a.getBytes(), b.getBytes());
if (order == sorter.FOLLOWS) {
changed = true;
data[j] = b;
data[j + 1] = a;
}
}
}
}
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
Sorting s = new Sorting();
print(data);
s.sortResults();
System.out.println("\n");
print(data);
}
static void print(String[] arg) {
for (String item : arg) {
System.out.println(item);
}
}
}