problems: add peeking iterator

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/peeking-iterator.java

@@ -0,0 +1,32 @@
+class PeekingIterator implements Iterator<Integer> {
+    private Iterator<Integer> it;
+
+    private Integer pVal;
+    private boolean pHasNext;
+
+    public PeekingIterator(Iterator<Integer> iterator) {
+        it = iterator;
+        next();
+    }
+
+    public Integer peek() {
+        return pVal;
+    }
+
+    @Override
+    public Integer next() {
+        pHasNext = it.hasNext();
+
+        Integer oldValue = pVal;
+        if (pHasNext) {
+            pVal = it.next();
+        }
+
+        return oldValue;
+    }
+
+    @Override
+    public boolean hasNext() {
+        return pHasNext;
+    }
+}