title: Create and classify new instance Weka
body: <p>I've created a Decision Tree (J48) using Weka API and Java. First I train my decision tree using an arff file.</p>
  
  <pre><code>public static void Tree(String Path) throws Exception {//Path path for the arff file
      J48 tree = new J48();         // new instance of tree
      DataSource source = new DataSource(Path);
      Instances data = source.getDataSet();
      // setting class attribute if the data format does not provide this information
      // For example, the XRFF format saves the class attribute information as well
      if (data.classIndex() == -1) {
          data.setClassIndex(data.numAttributes() - 1);
      }
      tree.buildClassifier(data);
      System.out.println(tree.toString());
  }
  </code></pre>
  
  <p>The used arff file includes 780 instances. Each instance has 6 attributes {PT1, w1, d1, PT2, w2, d2} all numeric and a class {yes, no}.
  My code is working and I can see the resulting Decision Tree using</p>
  
  <pre><code>System.out.println(tree.toString());
  </code></pre>
  
  <p>Now, I want to create a new Instance (not using another arff file) and classify this new instance. Say the values for this new instance are, for example, {50, 5, 800, 74, 3, 760}. Then the Decision Tree must return the corresponding class (a "yes" or a "no").</p>