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I'm pretty new to java and don't really know about these stuff and it's my first time writing these methods! of course I have no clue how I can write them.

will you check my Method and let me know what i'm doing wrong? thank you.

public static void sortByVehicleMakeModel(Vehicle[] vehicles) {
    boolean swapped = true;

    for(int y = 0; y < vehicles.length && swapped; y++) {
        for(int x = 0; x < vehicles.length - (y+1); x++) {
            if(vehicles[x].getMake() && vehicles[x].getModel().compareTo(vehicles[x + 1].getMake() && vehicles[x].getModel())) {    
                swap(vehicles, x, x + 1);

My error is on the second statemnet .compareto() The operator && is undefined for the argument type(s) java.lang.String, java.lang.String

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closed as off topic by Corbin, dreza, Brian Reichle, Trevor Pilley, svick Nov 17 '12 at 11:54

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umm, this question is probably best asked on SO if you are looking for help on why it's not working. Otherwise have you tried + instead of && –  dreza Nov 17 '12 at 6:17
What are you trying to do? It's really not clear. –  Nick ODell Nov 17 '12 at 6:26
@dreza what do you think about this: if(vehicles[x].getMake().compareTo(vehicles[x + 1].getMake()) > 0 && vehicles[x].getModel().compareTo(vehicles[x + 1].getModel()) > 0 ) { –  Niloo Rad Nov 17 '12 at 6:38
@NilooRad seems a better approach. I assume that at least it doesn't error now. If so perhaps you might like to adjust your question for getting assistance with actually reviewing the code... –  dreza Nov 17 '12 at 6:50

1 Answer 1

up vote 1 down vote accepted

There are probably better approaches as my knowledge Java is a bit limited but have you considered the Array.sort implementation?

Using that you might do something like:

public void sortByVehicleMakeModel(Vehicle[] vehicles) {  
    Arrays.sort(vehicles, new VehicleComparator());

class VehicleComparator implements Comparator<Vehicle> {

    public int compare(Vehicle v1, Vehicle v2) {
         return getMakeModel(v1).compareTo(getMakeModel(v2));

    private String getMakeModel(Vehicle v) {
        return v.getMake() + v.getModel();
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nice one thank you :) –  Niloo Rad Nov 17 '12 at 7:30

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