implementazione di linked tree. manca il tostring

exceptions/NonEmptyTreeException.java

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+package exceptions;
+
+/**
+ * Signals that the boundaries of a data structure have been illegally
+ * traversed (e.g. past the end of a list).
+ * @author Roberto Tamassia
+ */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
+
+public class NonEmptyTreeException extends RuntimeException {
+  public NonEmptyTreeException(String message) {
+    super (message);
+  }
+    public NonEmptyTreeException() {
+        super ("Tree already has a root");
+    }
+}

exceptions/UndeletableNodeException.java

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+package exceptions;
+
+/**
+ * Created with MONSTER.
+ * User: xgiovio
+ * Date: 05/03/14
+ * Time: 0.09
+ */
+public class UndeletableNodeException extends RuntimeException {
+
+    public UndeletableNodeException(){
+        super("Undeletable Node");
+    }
+    public UndeletableNodeException(String msg){
+        super(msg);
+    }
+}