String Binary Search Tree

Question

I'm facing a problem with my binary search tree. After add in all the String value, I am able to search what I have searched before. But, it cant retrieve the value stored in tree.right(or tree.left). Even if my tree.right have the value, but when I search it, it will return "Record Not Found". Output and Code shown below:

  public void add(String value) {  
      if(value.toLowerCase().equals("red") || value.toLowerCase().equals("green")  || value.toLowerCase().equals("blue") || 
            value.toLowerCase().equals("yellow") || value.toLowerCase().equals("black")) {
         if (root == null) {
            root = new StringTreeNode(value.toLowerCase());
            size ++;
        }
        else
            addleaf(root, value.toLowerCase());
    }

}


public void addleaf(StringTreeNode branch, String value) {
    if(value.compareTo(branch.data) < 0) {
        if (branch.left == null) {
            branch.left = new StringTreeNode(value);
            size ++;
        } else
            addleaf(branch.left, value);
    } else if (value.compareTo(branch.data) > 0) {
        if (branch.right == null) {
            branch.right = new StringTreeNode(value);
            size ++;
        } else
            addleaf(branch.right, value);
    } else {

    } 
}

public void searchNode (String value) {
    found = false;
    if(root == null)
        System.out.println("Nothing here");
    else
        searchBranch(root, value.toLowerCase());
    if (!found)
        System.out.println("Records not found.");
}


public void searchBranch (StringTreeNode tmp, String value) {
        if(value.equals(tmp.data)) {
            System.out.println("Records found, " + value + " exist in search history!");
            found = true;
        } else if (tmp.left != null)
            searchBranch(tmp.left, value);
        else if (tmp.right != null)
            searchBranch(tmp.right, value);
}

Output

What do you want to search?(0 to exit) : red

What do you want to search?(0 to exit) : green

What do you want to search?(0 to exit) : blue

What do you want to search?(0 to exit) : yellow

What do you want to search?(0 to exit) : black

What do you want to search?(0 to exit) : 0

Tree Value : red green blue black yellow

Stack Value : 1. black 2. yellow 3. blue 4. green 5. red

What do you want to search for the existence history?(0 to exit) : red

Records found, red exist in search history!

What do you want to search for the existence history?(0 to exit) : green

Records found, green exist in search history!

What do you want to search for the existence history?(0 to exit) : blue

Records found, blue exist in search history!

**What do you want to search for the existence history?(0 to exit) : yellow

Records not found.**

What do you want to search for the existence history?(0 to exit) : black

Records found, black exist in search history!

I am curious although "yellow" is added into tree, but "yellow" is not in my search result.

Answer 1

Your searchBranch method is using the wrong criteria to decide which child branch to search. It should be comparing tmp.data to value to decide between the left and right branches, not just going down whichever branch happens to lead somewhere:

public void searchBranch (StringTreeNode tmp, String value) {    
    if(value.equals(tmp.data)) {
        System.out.println("Records found, " + value + " exist in search history!");
        found = true;
    } else if (value.compareTo(tmp.data) < 0)
        searchBranch(tmp.left, value);
    else 
        searchBranch(tmp.right, value);
}

Notice that this is basically the same logic that addLeaf uses when deciding whether a given value belongs in the left or right branch of a node.