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Answer:

No. The statement could be written as follows. The toString() method will automatically be called:

if ( tree0 != null ) str += "Tree 0: " + tree0 + "\n";

More Methods

A Forest object might need an area() method. This might be useful if you were modeling a real forest and needed to know how much CO2 the forest was absorbing. Here is the class, with more blanks:

 
// Forest.java
//
public class Forest
{
  // instance variables
  private Tree tree0=null, tree1=null, tree2=null, tree3=null;
  
  // methods
  public void setTree( int treeNum, Tree tree ) 
  public Tree getTree( int treeNum )
  public String toString()
  
  public double area()
  {
      
  }
  
  public double volume()
  {
      
  }

}  

QUESTION 17:

Fill in the methods. Beware: some of the Tree reference variables might be null.


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