Added filter

1 files changed, 43 insertions, 0 deletions

diff --git a/model-data/src/main/java/org/eclipse/viatra/solver/data/util/CollectionsUtil.java b/model-data/src/main/java/org/eclipse/viatra/solver/data/util/CollectionsUtil.java
index d950228d..7b6bf9b3 100644
--- a/model-data/src/main/java/org/eclipse/viatra/solver/data/util/CollectionsUtil.java
+++ b/model-data/src/main/java/org/eclipse/viatra/solver/data/util/CollectionsUtil.java
@@ -1,7 +1,9 @@
 package org.eclipse.viatra.solver.data.util;
 
 import java.util.Iterator;
+import java.util.NoSuchElementException;
 import java.util.function.Function;
+import java.util.function.Predicate;
 
 public final class CollectionsUtil {
         private CollectionsUtil() {
@@ -26,4 +28,45 @@ public final class CollectionsUtil {
         static <S,T> Iterable<T> map(Iterable<S> source, Function<S, T> transformation) {
                 return (()->map(source.iterator(),transformation));
         }
+        
+        static <T> Iterator<T> filter(Iterator<T> source, Predicate<T> condition) {
+                return new Iterator<T>() {
+                        T internalNext = move();
+                        boolean internalHasNext;
+                        
+                        private T move() {
+                                internalHasNext = source.hasNext();
+                                if(internalHasNext) {
+                                        internalNext = source.next();
+                                }
+                                while(internalHasNext && !condition.test(internalNext)) {
+                                        internalHasNext = source.hasNext();
+                                        if(internalHasNext) {
+                                                internalNext = source.next();
+                                        }
+                                }
+                                return internalNext;
+                        }
+
+                        @Override
+                        public boolean hasNext() {
+                                return internalHasNext;
+                        }
+
+                        @Override
+                        public T next() {
+                                if(!internalHasNext) {
+                                        throw new NoSuchElementException();
+                                } else {
+                                        T result = internalNext;
+                                        move();
+                                        return result;
+                                }
+                        }
+                };
+        }
+        
+        static <T> Iterable<T> filter(Iterable<T> source, Predicate<T> condition) {
+                return (()->filter(source.iterator(),condition));
+        }
 }