CODEWITHSUNDEEP
javastringbinary-treepolymorphism
jun
jun

Reputation: 1

polymorphic binary search tree

I have 2 classes, NonEmptyTree and EmptyTree that implement the Tree interface. toString() method in NonEmptyTree class should return a string: key=>value key=>value key>value etc... I do not know how to remove last space at end of result. EDIT: I cannot use any methods in the String class, and I cannot compare anything to null. 

public String toString() {
        String result = "";
        result+=(this.left.toString());
        result+=this.key;
        result+="=>";
        result+=this.value;
        result+=" ";
        result+=this.right.toString();
        return result;
    }

I've tried having a variable for the class that indicates if a NonEmptyTree instance is the largest in the current tree, but console displayed same string.

for example, the string would look like this:

"7=>seven 10=>ten 12=>twelve 15=>fifteen 16=>sixteen 17=>seventeen 20=>twenty 30=>thirty "

any help would be appreciated. thanks

Upvotes: 0

Views: 2827

Answers (3)

Matt
Matt

Reputation: 3736

Can you simply add an 'if'? See below:

public String toString() 
{ 
    String result = ""; 
    result+=(this.left.toString());
    result+=this.key; result+="=>";
    result+=this.value; 
    if (this.right!=null)  // Just add this, so it doesn't add an extra space if no right result exists
    {
        result+=" ";
        result+=this.right.toString();
    }
    return result; 
}

Upvotes: 1

Brian Roach
Brian Roach

Reputation: 76898

public String toString() {
    StringBuilder result = new StringBuilder();
    result.append(this.left.toString());
    result.append(this.key);
    result.append("=>");
    result.append(this.value);
    result.append(" ");
    result.append(this.right.toString());
    return result.toString().trim();
}

Upvotes: 2

pajton
pajton

Reputation: 16226

Use String.trim():

return result.trim()

BTW. if you do a lot of String additions it's better to use StringBuilder and its method append() instead of adding multiple Strings with +.

Upvotes: 2

Related Questions