java - 3 dimensional ConcurrentSkipListMap map -

i have written 3 dimensional concurrentskiplistmap, not able figure out way iterate on it. how define iterator same.

import java.util.concurrent.concurrentskiplistmap; /**  * helper implementation handle 3 dimensional sorted maps  */ public class mycustomindex {     private concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], byte[]>>> table;      public mycustomindex() {         this.table = new concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], byte[]>>>(new customcomparator);      }     /**      *       * @param k      * @param f      * @param q      */     public void put(byte[] k, byte[] f, byte[] q) {         concurrentskiplistmap<byte[], byte[]> qtodummyvaluemap;          concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], byte[]>> ftoqmap;          if( table.containsk(k)) {             ftoqmap = table.get(k);             if ( ftoqmap.containsk(f)) {                 qtodummyvaluemap = ftoqmap.get(f);             } else {                 qtodummyvaluemap = new concurrentskiplistmap<byte[], byte[]>(new customcomparator);              }         } else {             qtodummyvaluemap = new concurrentskiplistmap<byte[], byte[]>(new customcomparator);             ftoqmap = new concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], byte[]>>(new customcomparator);         }                qtodummyvaluemap.put(q, new byte[0]);         ftoqmap.put(f, qtodummyvaluemap);         table.put(k, ftoqmap);     }      public concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], byte[]>>> gettable() {         return table;     }     public void settable(             concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], concurrentskiplistmap<byte[], byte[]>>> table) {         this.table = table;     }  } 

here's nested iterator take iterator<iterator<t>> , turn iterator<t>. there static methods allow grow iterator<v> objects out of map<k,v>s along higher-order stuff (iterator<iterator<v>> , map<k,map<k,v> etc.).

the idea iterating on higher levels of iterator such iterator<iterator<iterator<t>>> wrap 1 of these inside other can see in three-way test , mapmapmap test.

public class nestediterator<t> implements iterator<t> {   // outer iterator. goes null when exhausted.   iterator<iterator<t>> i2 = null;   // inner iterator. goes null when exhausted.   iterator<t> i1 = null;   // next value.   t next = null;    // takes depth-2 iterator.   public nestediterator(iterator<iterator<t>> i2) {     this.i2 = i2;     // prime pump.     if (i2 != null && i2.hasnext()) {       i1 = i2.next();     }   }    @override   public boolean hasnext() {     // there 1 waiting?     if (next == null) {       // no!       // i1 go null if exhausted.       if (i1 == null) {         // i1 exhausted! new 1 i2.         if (i2 != null && i2.hasnext()) {           /// next.           i1 = i2.next();           // set i2 null if exhausted.           if (!i2.hasnext()) {             // exhausted.             i2 = null;           }         } else {           // exhausted.           i2 = null;         }       }       // null i1 mean over!       if (i1 != null) {         if (i1.hasnext()) {           // next.           next = i1.next();           // set i1 null if exhausted.           if (!i1.hasnext()) {             // exhausted.             i1 = null;           }         } else {           // exhausted.           i1 = null;         }       }     }     return next != null;   }    @override   public t next() {     t n = next;     next = null;     return n;   }    @override   public void remove() {     throw new unsupportedoperationexception("not supported.");   }    // iterating across maps of maps of maps.   static <k1, k2, k3, v> iterator<iterator<iterator<v>>> iiiv(map<k1, map<k2, map<k3, v>>> i) {     final iterator<map<k2, map<k3, v>>> iv = iv(i);     return new iterator<iterator<iterator<v>>>() {       @override       public boolean hasnext() {         return iv.hasnext();       }        @override       public iterator<iterator<v>> next() {         return iiv(iv.next());       }        @override       public void remove() {         iv.remove();       }     };   }    // iterating across maps of maps.   static <k1, k2, v> iterator<iterator<v>> iiv(map<k1, map<k2, v>> i) {     final iterator<map<k2, v>> iv = iv(i);     return new iterator<iterator<v>>() {       @override       public boolean hasnext() {         return iv.hasnext();       }        @override       public iterator<v> next() {         return iv(iv.next());       }        @override       public void remove() {         iv.remove();       }     };   }    // iterating across map values.   static <k, v> iterator<v> iv(final map<k, v> map) {     return iv(map.entryset().iterator());   }    // iterating across map.entry iterators.   static <k, v> iterator<v> iv(final iterator<map.entry<k, v>> i) {     return new iterator<v>() {       @override       public boolean hasnext() {         return i.hasnext();       }        @override       public v next() {         return i.next().getvalue();       }        @override       public void remove() {         i.remove();       }     };   }    // **** testing ****   enum {     i1, i2, i3;   };    public static void main(string[] args) {     // 2 way test.     testtwoway();     system.out.flush();     system.err.flush();     // 3 way test.     testthreeway();     system.out.flush();     system.err.flush();     // mapmap test     testmapmap();     system.out.flush();     system.err.flush();     // mapmapmap test     testmapmapmap();     system.out.flush();     system.err.flush();   }    private static void testmapmap() {     map<string,string> m = new treemap<> ();     m.put("m-1", "v-1");     m.put("m-2", "v-2");     map<string,map<string,string>> mm = new treemap<> ();     mm.put("mm-1", m);     mm.put("mm-2", m);     system.out.println("mapmap");     iterator<iterator<string>> iiv = iiv(mm);     (iterator<string> = new nestediterator<>(iiv); i.hasnext();) {       system.out.print(i.next() + ",");     }     system.out.println();   }    private static void testmapmapmap() {     map<string,string> m = new treemap<> ();     m.put("m-1", "v-1");     m.put("m-2", "v-2");     m.put("m-3", "v-3");     map<string,map<string,string>> mm = new treemap<> ();     mm.put("mm-1", m);     mm.put("mm-2", m);     map<string,map<string,map<string,string>>> mmm = new treemap<> ();     mmm.put("mmm-1", mm);     mmm.put("mmm-2", mm);     system.out.println("mapmapmap");     iterator<iterator<iterator<string>>> iiiv = iiiv(mmm);     (iterator<string> = new nestediterator<>(new nestediterator<>(iiiv)); i.hasnext();) {       system.out.print(i.next() + ",");     }     system.out.println();   }    private static void testthreeway() {     // 3 way test.     system.out.println("three way");     list<iterator<i>> lii1 = arrays.aslist(             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator());     list<iterator<i>> lii2 = arrays.aslist(             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator());     list<iterator<i>> lii3 = arrays.aslist(             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator());     iterator<iterator<iterator<i>>> liii = arrays.aslist(             lii1.iterator(),             lii2.iterator(),             lii3.iterator()).iterator();     // grow 3-nest.     // unroll it.     (iterator<i> ii = new nestediterator<>(new nestediterator<>(liii)); ii.hasnext();) {       = ii.next();       system.out.print(it + ",");     }     system.out.println();   }    private static void testtwoway() {     system.out.println("two way");     list<iterator<i>> lii = arrays.aslist(             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator(),             enumset.allof(i.class).iterator());     (iterator<i> ii = new nestediterator<>(lii.iterator()); ii.hasnext();) {       = ii.next();       system.out.print(it + ",");     }     system.out.println();   } } 

your code can this. note have not tested @ , have made use of map instead of concurrentskiplistmap whenever possible , using <> stuff java 7 out lot.

public class mycustomindex  implements iterable<byte[]> {   private map<byte[], map<byte[], map<byte[], byte[]>>> table;    public mycustomindex() {     this.table = new concurrentskiplistmap<>();   }    /**    * @param k    * @param f    * @param q    */   public void put(byte[] k, byte[] f, byte[] q) {     map<byte[], byte[]> qtodummyvaluemap;     map<byte[], map<byte[], byte[]>> ftoqmap;      if (table.containskey(k)) {       ftoqmap = table.get(k);       if (ftoqmap.containskey(f)) {         qtodummyvaluemap = ftoqmap.get(f);       } else {         qtodummyvaluemap = new concurrentskiplistmap<>();       }     } else {       qtodummyvaluemap = new concurrentskiplistmap<>();       ftoqmap = new concurrentskiplistmap<>();     }     qtodummyvaluemap.put(q, new byte[0]);     ftoqmap.put(f, qtodummyvaluemap);     table.put(k, ftoqmap);   }    public map<byte[], map<byte[], map<byte[], byte[]>>> gettable() {     return table;   }    public iterator<byte[]> iterator () {     // **** have been aiming @ along ****     return new nestediterator(new nestediterator<>(nestediterator.iiiv(table)));   }  }