#fixed code
                                public VerbalExpression replace(String source, String value) {
        this.updatePattern();
        this.source.replaceAll(pattern,value);
        return this;
    }
#vulnerable code 
                                public VerbalExpression replace(String source, String value) {
        this.add("");
        this.source.replaceAll(pattern,value);
        return this;
    } 
                            #location 3 
                            #vulnerability type NULL_DEREFERENCE