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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12. 		LRUCacheLHM<Integer, String> cache = new LRUCacheLHM<>(5);
  13.         System.out.println("In:quick"+" Out:"+cache.place(0, "quick"));
  14.         System.out.println("In:brown"+" Out:"+cache.place(1, "brown"));
  15.         System.out.println("In:fox"+" Out:"+cache.place(2, "fox"));
  16.         System.out.println("In:jumps"+" Out:"+cache.place(3, "jumps"));
  17.         System.out.println("In:over"+" Out:"+cache.place(4, "over"));
  18.         System.out.println("In:the"+" Out:"+cache.place(5, "the"));
  19.         System.out.println("In:lazy"+" Out:"+cache.place(6, "lazy"));
  20.         System.out.println("In:dog"+" Out:"+cache.place(7, "dog"));
  21. 	}
  22. }
  23.  
  24. class LRUCacheLHM<K,V> extends LinkedHashMap<K,V> {
  25.  
  26.     private int capacity;
  27.  
  28.     public LRUCacheLHM(int capacity) {
  29.         //1 extra element as add happens before remove (101), and load factor big
  30.         //enough to avoid triggering resize.  True = keep in access order.
  31.         super(capacity + 1, 1.1f, true);
  32.         this.capacity = capacity;
  33.     }
  34.     private ThreadLocal<Map.Entry<K,V>> removed = new ThreadLocal<Map.Entry<K,V>>();
  35.     private ThreadLocal<Boolean> report = new ThreadLocal<Boolean>();
  36.     {
  37.     	report.set(false);
  38.     }
  39.     @Override
  40.     public boolean removeEldestEntry(Map.Entry<K,V> eldest) {
  41.         boolean res = size() > capacity;
  42.         if (res && report.get()) {
  43.         	removed.set(eldest);
  44.         }
  45.         return res;
  46.     }
  47.     public Map.Entry<K,V> place(K k, V v) {
  48.     	report.set(true);
  49.     	put(k, v);
  50.     	try {
  51.     	    return removed.get();
  52.     	} finally {
  53.     	    removed.set(null);
  54.     	    report.set(false);
  55.     	}
  56.     }
  57.  
  58. }
Success #stdin #stdout 0.1s 320320KB
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stdin
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Standard input is empty
stdout
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In:quick Out:null
In:brown Out:null
In:fox Out:null
In:jumps Out:null
In:over Out:null
In:the Out:0=quick
In:lazy Out:1=brown
In:dog Out:2=fox
https://ideone.com/7INifi
language:
Java (HotSpot 12)
created:
9 years ago
visibility:
public

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