#vulnerable code 
                                protected void setExpression(String expression) {
        if (expression != null && !"".equals(expression)) {
            if ((this.expr = EX_PRECACHE.get(expression)) == null) {
                synchronized (EX_PRECACHE) {
                    length = (this.expr = expression.toCharArray()).length;

                    // trim any whitespace.
                    while (length != 0 && isWhitespace(this.expr[length - 1])) length--;

                    char[] e = new char[length];

                    for (int i = 0; i != e.length; i++)
                        e[i] = expr[i];

                    EX_PRECACHE.put(expression, e);
                }
            }
            else {
                length = this.expr.length;
            }
        }
    } 
                            #location 3 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                protected void setExpression(String expression) {
        if (expression != null && !"".equals(expression)) {
            synchronized (EX_PRECACHE) {
                if ((this.expr = EX_PRECACHE.get(expression)) == null) {
                    length = (this.expr = expression.toCharArray()).length;

                    // trim any whitespace.
                    while (length != 0 && isWhitespace(this.expr[length - 1])) length--;

                    char[] e = new char[length];

                    for (int i = 0; i != e.length; i++)
                        e[i] = expr[i];

                    EX_PRECACHE.put(expression, e);
                }
                else {
                    length = this.expr.length;
                }
            }

        }
    }