How to get unique indexes of a sorted Java ArrayList? -

i have arraylist need sort need indexes of sorted items too. arraylist has many duplicate values updated , indexex duplicate. need unique indexes. there way indexes?

indices = new int[depth.size()]; arraylist<float> fstore = new arraylist(depth); collections.sort(depth);  (int n=0; n<depth.size(); n++){         indices[n] = fstore.indexof(depth.get(n));       } 

the problem indexof() returns index of first occurrence of element in list, or -1 if not present. if list has duplicates, then, these duplicates, you'll index of first occurrence within list.

there many ways accomplish want. 1 use sortedset , helper indexedentry class:

public class indexedentry<t extends comparable<t>>     implements comparable<indexedentry<t>> {      private final integer index;      private final t entry;      public indexedentry(integer index, t entry) {         this.index = index;         this.entry = entry;     }      public integer getindex() {         return this.index;     }      public t getentry() {         return this.entry;     }      @override     public int compareto(indexedentry<t> other) {         int byentry = this.getentry().compareto(other.getentry());         if (byentry == 0) {             return this.getindex().compareto(other.getindex());         }         return byentry;     }      @override     public string tostring() {         return "(" + this.entry + ", " + this.index + ")";     } } 

the indexedentry class wraps comparable value , index, , implements comparable first comparing value, , if value equal, compares index. means ordered list of indexedentry have elements ordered (value, index).

to use indexedentry class, iterate on collection, create indexedentry each element wrapping element , index, , sort list of indexedentry:

    list<float> unordered = new arraylist<>(arrays.aslist(3.2f, 1.0f, 7.5f, 3.2f, 0.8f));     system.out.println(unordered); // [3.2, 1.0, 7.5, 3.2, 0.8]      list<indexedentry<float>> ordered = new arraylist<>();     (int = 0; < unordered.size(); i++) {         indexedentry<float> entry = new indexedentry<>(i, unordered.get(i));         ordered.add(entry);     }     collections.sort(ordered);     system.out.println(ordered); // [(0.8, 4), (1.0, 1), (3.2, 0), (3.2, 3), (7.5, 2)] 

once sorted, ordered list contain elements along original index.