Bug fix

src/PPJoin.java

@@ -382,7 +382,8 @@ public class PPJoin {
 					}
 				}
 				if (overlap >= alpha) {
-					this.similarRecords.putIfAbsent(x.id, y.id);
+					//this.similarRecords.putIfAbsent(x.id, y.id);
+					this.similarRecords.put(x.id, y.id);
 				}
 			}
 		}