大输入时字符串连接速度慢

像这样的弦乐伴奏速度非常慢。使用StringBuilder。

@Overridepublic String toString(){        StringBuilder buffer = new StringBuilder();        printTree(this, buffer);        return buffer.toString();}public void printTree(AbstractTree<E> tree, StringBuilder buffer){    if (tree.isLeaf()){        buffer.append(tree.getNodeName());    } else {        buffer.append(tree.getNodeName());        buffer.append("(");        int i = 0;        Iterator<AbstractTree<E>> child = tree.getChildren().iterator();        while (i < tree.getChildren().size() - 1){ printTree(child.next(), buffer); buffer.append(", "); i++;        }        printTree(child.next(), buffer);         buffer.append(")");    }}