Added the predicate implementation 'PredicateContains'; allows for ex…

…tracting the underling java collection.

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

@@ -0,0 +1,64 @@
+package org.aksw.commons.util.function;
+
+import java.io.Serializable;
+import java.util.Collection;
+import java.util.Objects;
+import java.util.Set;
+import java.util.function.Predicate;
+
+/**
+ * A predicate to test containment in the backing collection.
+ * Allows for casting and unwrapping the items.
+ */
+public class PredicateContains<T>
+    implements Predicate<T>, Serializable
+{
+    private static final long serialVersionUID = 1L;
+    protected Collection<T> items;
+
+    protected PredicateContains(Collection<T> items) {
+        super();
+        this.items = Objects.requireNonNull(items);
+    }
+
+    public static <T> Predicate<T> of(T item) {
+        return of(Set.of(item));
+    }
+
+    public static <T> Predicate<T> of(Collection<T> items) {
+        return new PredicateContains<>(items);
+    }
+
+    public Collection<T> getItems() {
+        return items;
+    }
+
+    @Override
+    public boolean test(T item) {
+        boolean result = items.contains(item);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "test if x in " + items;
+    }
+
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(items);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        PredicateContains<?> other = (PredicateContains<?>) obj;
+        return Objects.equals(items, other.items);
+    }
+}