Slow string concatenation over large input

Question

I\'ve written an n-ary tree ADT which works fine. However, I need to store its serialization in a variable a calling class. eg.

    DomTree a         


        

Answer 1

String concats like that are punishingly slow. Use a StringBuilder.

@Override
public String toString(){
        StringBuilder buffer = new StringBuilder();
        printTree(this, buffer);
        return buffer.toString();
}

public void printTree(AbstractTree tree, StringBuilder buffer){
    if (tree.isLeaf()){
        buffer.append(tree.getNodeName());
    } else {
        buffer.append(tree.getNodeName());
        buffer.append("(");

        int i = 0;
        Iterator> child = tree.getChildren().iterator();
        while (i < tree.getChildren().size() - 1){
            printTree(child.next(), buffer);
            buffer.append(", ");
            i++;
        }
        printTree(child.next(), buffer); 
        buffer.append(")");
    }
}