在不使用集合的情况下在Java中对多维数组进行排序

Question

String Name[][]={
    {"prakash","kumar"},
    {"raj","kappor"},
    {"vinod","bhart"},
    {"yraj","tkappor"},                         
    {"avinod","fbhart"}
};

Can we sort this string array surname first, then firstname without using collections ?

Answer 1

You can sort the arrays in place using java.util.Arrays utility class. In this case it would look something like this:

    Arrays.sort(Name, new Comparator<String[]>(){
        int LASTNAME=0, FIRSTNAME=1;

        @Override
        public int compare(String[] o1, String[] o2) {
            int c = o1[LASTNAME].compareTo(o2[LASTNAME]);
            if (c != 0) return c;
            return o1[FIRSTNAME].compareTo(o2[FIRSTNAME]);
        }
    });

Answer 2

You can use <T> Arrays.sort(T[] a, Comparator<? super T> c) (see here ) to sort generic arrays and specify a custom comparator that in your case compares two String[] by looking first at the surname and then at the first name (See Panu's answer for a possible implementation).

If you don't want to use Arrays either, you will have to implement a sorting algorithm yourself. You can find a good overview of sorting algorithms here . In order to use your custom comparison you will have to adapt the comparison methods.

Answer 3

Arrays.sort(Name, ComparatorFactory.compareOn(ON.FIRSTNAME));

enum ON {
    FIRSTNAME, LASTNAME, FULLNAME }

class ComparatorFactroy {
    static Comparator compareOn(ON on){
        switch (on) {
            case FIRSTNAME :
                return new Comparator<String[]>() {
                            @Override
                            public int compare(String[] tar) { ... }
                };
            case LASTNAME :
                return.....
            default:
                return ...
            }
}

Answer 4

final String[][] data = new String[][] {
            new String[] { "prakash","kumar" },
            new String[] { "raj","kappor" },
            new String[] { "vinod","bhart" },
            new String[] { "yraj","tkappor" },
            new String[] { "avinod","fbhart" }};

    Arrays.sort(data, new Comparator<String[]>() {
        @Override
        public int compare(final String[] entry1, final String[] entry2) {
            final String time1 = entry1[0];
            final String time2 = entry2[0];
            return time1.compareTo(time2);
        }
    });

Answer 5

If you do not want to use java's inbuilt sorting mechanism then you can implement one yourself something like this:

    for(int i=0;i<Name.length;i++) {
        for(int j=i+1;j<Name.length;j++) {
            if(Name[i][1].compareTo(Name[j][1])>0) {
                String[] temp = Name[i];
                Name[i] = Name[j];
                Name[j] = temp;
            }
        }
    }

Hope this helps.