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HashPool.java

package gov.nasa.arc.ase.util;

import java.util.Hashtable;
//#ifdef JDK11



//#else JDK11
import java.util.Set;
import java.util.TreeSet;
import java.util.Iterator;
//#endif JDK11

public class HashPool {
  public class PoolEntry implements Comparable {
    private Object obj;
    private int idx;

    public PoolEntry(Object o, int i) {
      obj = o;
      idx = i;
    }

    public Object getObject() {
      return obj;
    }

    public int getIndex() {
      return idx;
    }

    public int hashCode() {
      return idx;
    }

    public boolean equals(Object obj) {
      PoolEntry other = (PoolEntry)obj;
      return (other.idx == idx);
    }

    public String toString() {
      return idx + " => " + obj;
    }

    public int compareTo(Object o) {
      PoolEntry other = (PoolEntry)o;
      return (idx - other.idx);
    }
  }

  private Hashtable pool;
  private int size;
  private int length;
  private Object[] objects;
  private static final int DELTA = 10;

  public HashPool() {
    pool  = new Hashtable();
    objects = new Object[length = DELTA];
    objects[0] = null;
    size = 1;
  }  
  public Object get(Object o) {
    if(o == null) return null;
    PoolEntry e = (PoolEntry)pool.get(o);
    if (e != null) return e.obj;

    return put(o).obj;
  }  
  public PoolEntry getEntry(Object o) {
    if(o == null) return null;
    PoolEntry e = (PoolEntry)pool.get(o);
    if (e != null) return e;

    return put(o);
  }  
  public int getIndex(Object o) {
    if(o == null) return -1;
    PoolEntry e = (PoolEntry)pool.get(o);
    if (e != null) return e.idx;

    return put(o).idx;
  }  
  public Object getObject(int idx) {
    return objects[idx];
  }  
  public synchronized void print() {
    System.out.println("{");

//#ifdef JDK11

//#else JDK11
    Set s = new TreeSet(pool.values());
//#endif JDK11

    for(Iterator i = s.iterator(); i.hasNext(); ) {
      Object entry = i.next();
      System.out.println("\t" + entry);
    }
    System.out.println("}");
  }  
  public synchronized PoolEntry put(Object o) {
    PoolEntry e = (PoolEntry)pool.get(o);
    if(e != null) return e;

    if(length < size+1) {
      Object[] newObjects = new Object[length+DELTA];
      System.arraycopy(objects, 0, newObjects, 0, length);
      objects = newObjects;
      length += DELTA;
    }
    objects[size] = o;
    pool.put(o, e = new PoolEntry(o, size++));

    return e;
  }  
  public synchronized int size() {
    return size;
  }  
}

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