Introduction to Binary Trees - Advanced Topics in Java: Core Concepts in Data Structures - page 233

class NodeData {
String word;
int freq;
public NodeData(String w) {
word = w;
freq = 0;
}
public void incrFreq() {
++freq;
}
public int compareTo(NodeData d) {
return this.word.compareTo(d.word);
}
public void visit() {
WordFrequencyBST.out.printf("%-15s %2d\n", word, freq);
}
} //end class NodeData
// class TreeNode goes here
// class BinaryTree (with findOrInsert added) goes here
Note that in and out are declared as static class variables. This is not necessary for in , which could have been
declared in main since it is used only there. However, the visit method of the NodeData class needs to know where to
send the output, so it needs access to out . We give it access by declaring out as a class variable.
Since findOrInsert requires a NodeData object as its argument, we must create a NodeData object from word
before calling it in this statement:
TreeNode node = bst.findOrInsert(new NodeData(word));
An in-order traversal of the search tree yields the words in alphabetical order.
Suppose the file wordFreq.in contains the following data:
If you can trust yourself when all men doubt you;
If you can dream - and not make dreams your master;
If you can talk with crowds and keep your virtue;
If all men count with you, but none too much;
If neither foes nor loving friends can hurt you;