title: I have an error about using class and objects
body: <pre><code>public final class Set implements ASet {
  Integer[] NewSet;
  
      public void Set() {
      }
  
      @Override
      public void insert(int value) {
          for (int i=0; i&lt;9; i++) {
              if (this.NewSet[i] == value) {
                  break;
              }
              else {
                  this.NewSet[9] = value;
              }
          }
      }
  
      @Override
      public void union(ASet set) {
          for (int j=0; j&lt;10; j++) {
              this.insert(set.NewSet[j]);
          }
      }
  
      @Override
      public int[] show() {
          return Array.from(this.NewSet);
      }
  }
  </code></pre>
  <p>I want to insert the interger.
  When I compile it, there is an error:</p>
  <pre><code>error: cannot find symbol
          this.insert(set.NewSet[j]);
                         ^
    symbol:   variable NewSet
    location: variable set of type ASet
  </code></pre>
  <p>And I want to return the elements of the object as an array by show() method, but there is another error:</p>
  <pre><code>error: cannot find symbol
      return Array.from(this.NewSet);
                  ^
    symbol:   method from(Integer[])
    location: class Array
  </code></pre>