implement iterator for BValue, add exception class

src/main/java/com/mykola2312/retracker/bencode/BValue.java

@@ -1,6 +1,15 @@
 package com.mykola2312.retracker.bencode;
 
-abstract public class BValue {
+import java.util.Iterator;
+
+/* Base class for every type of bencode value, as tree nodes,
+ * simple types like integer or string will have next pointing
+ * to next sibling and have no child, where list's child points
+ * to linked values - items of list. In dict situation, child points
+ * to linked list of keys, where each key has child - value
+ */
+
+abstract public class BValue implements Iterable<BValue> {
 	private BType type;
 	private BValue next = null;
 	private BValue child = null;
@@ -20,4 +29,8 @@ abstract public class BValue {
 	public BValue getChild() {
 		return child;
 	}
+	
+	public Iterator<BValue> iterator() {
+		return new BValueIterator(child);
+	}
 }

src/main/java/com/mykola2312/retracker/bencode/BValueIterator.java

@@ -0,0 +1,19 @@
+package com.mykola2312.retracker.bencode;
+
+import java.util.Iterator;
+
+public class BValueIterator implements Iterator<BValue> {
+	private BValue node;
+	public BValueIterator(BValue head) {
+		this.node = head;
+	}
+	
+	public boolean hasNext() {
+		return node != null && node.getNext() != null;
+	}
+	
+	public BValue next() {
+		node = node.getNext();
+		return node;
+	}
+}

src/main/java/com/mykola2312/retracker/bencode/error/BError.java

@@ -0,0 +1,14 @@
+package com.mykola2312.retracker.bencode.error;
+
+import com.mykola2312.retracker.bencode.BValue;
+
+public class BError extends Exception {
+	private static final long serialVersionUID = 6950892783320917930L;
+
+	public BValue node;
+	
+	public BError(BValue node, String message) {
+		super(message);
+		this.node = node;
+	}
+}

src/main/java/com/mykola2312/retracker/bencode/error/BErrorNoChildren.java

@@ -0,0 +1,11 @@
+package com.mykola2312.retracker.bencode.error;
+
+import com.mykola2312.retracker.bencode.BValue;
+
+public class BErrorNoChildren extends BError {
+	private static final long serialVersionUID = -4503679050993811843L;
+
+	public BErrorNoChildren(BValue node) {
+		super(node, "Node has no children");
+	}
+}