public void displayTree() 
    {
        if (this.isLeaf()) {
            System.out.print("(" + this.caractere + ":" + this.poids + ")");
        }
        else {
            System.out.print("(");
            this.fGauche.displayTree();
            this.fDroit.displayTree();
            System.out.print(")");
        }
    }