jtulach@315: package org.apidesign.javamonitorflaws;
jtulach@315: 
jtulach@315: import java.util.HashMap;
jtulach@315: import java.util.Map;
jtulach@315: 
jtulach@315: /**
jtulach@315:  *
jtulach@315:  * @author Jaroslav Tulach <jtulach@netbeans.org>
jtulach@315:  */
jtulach@315: public abstract class Cache<From,To> {
jtulach@315:     private Map<From,To> cache;
jtulach@315: 
jtulach@315:     public final To get(From f) {
jtulach@315:         for (;;) {
jtulach@315:             synchronized (this) {
jtulach@315:                 if (cache == null) {
jtulach@315:                     cache = new HashMap<From, To>();
jtulach@315:                 }
jtulach@315:                 To t = cache.get(f);
jtulach@315:                 if (t != null) {
jtulach@315:                     return t;
jtulach@315:                 }
jtulach@315:             }
jtulach@315: 
jtulach@315:             To newT = createItem(f);
jtulach@315: 
jtulach@315:             synchronized (this) {
jtulach@315:                 To t = cache.get(f);
jtulach@315:                 if (t == null) {
jtulach@315:                     cache.put(f, newT);
jtulach@315:                     return newT;
jtulach@315:                 } else {
jtulach@315:                     return t;
jtulach@315:                 }
jtulach@315:             }
jtulach@315:         }
jtulach@315:     }
jtulach@315: 
jtulach@315:     protected abstract To createItem(From f);
jtulach@315: }