Added FixpointIterator to utils (function package)

aksw-commons-utils-parent/aksw-commons-utils/src/main/java/org/aksw/commons/util/function/FixpointIteration.java

@@ -0,0 +1,45 @@
+package org.aksw.commons.util.function;
+
+import java.util.Objects;
+import java.util.function.Function;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class FixpointIteration {
+
+    private static Logger logger = LoggerFactory.getLogger(FixpointIteration.class);
+
+    public static <T> Function<T, T> createClosure(Function<? super T, ? extends T> transform) {
+        return op -> apply(op, transform);
+    }
+
+    public static <T> T apply(T op, Function<? super T, ? extends T> transform) {
+        T current;
+        do {
+            current = op;
+            op = transform.apply(current);
+        } while(!current.equals(op));
+
+        return current;
+    }
+
+    public static <T> T apply(int max, T init, Function<? super T, ? extends T> fn) {
+        T result = init;
+
+        int i = 0;
+        for(; i < max; ++i) {
+            T tmp = fn.apply(result);
+            if(Objects.equals(tmp, result)) {
+                break;
+            }
+            result = tmp;
+        }
+
+        if(i >= max) {
+            logger.warn("Fixpoint iteration reached iteration threshold");
+        }
+
+        return result;
+    }
+}