calculating static expression in java

I wanted to calculate static expression in java. something is wrong so I get the wrong answer. but I can’t figure out where is the problem.

”’

 public static void main(String[] args) {
        String input = "3x^2+4x^3+6";
        // calculate the value when x is 3
        String[] expression=input.split("\\+"); //spltting the expression in 3 parts
        
        String[] firstpart=expression[0].split(""); //splitting every part
        String[] secondpart=expression[1].split("");
        String[] thirdpart=expression[2].split("");
        
        int sum3=Integer.valueOf(thirdpart[0]);
        
        int sum1=0;
        int i=0;
        while(i<firstpart.length){
            
                if("^".equals(firstpart[i])){
                    sum1+=(Integer.valueOf(secondpart[i-2]))*(Math.pow(3,(Integer.valueOf(secondpart[i+1]))));
                                     //3                    * 3^2
                }
            i++;
        }
        
        
        int sum2=0;
        int k=0;
        while(k<secondpart.length){    
        if("^".equals(secondpart[k])){
            sum2+=(Integer.valueOf(secondpart[k-2]))*(Math.pow(3,(Integer.valueOf(secondpart[k+1]))));
            //              4                       * 3^3
            }
        k++;}
        
        System.out.println(sum1);
        System.out.println(sum2);
        System.out.println(sum3);
        System.out.println(sum1+sum2+sum3);

}
”’

>Solution :

while(i<firstpart.length){
        
            if("^".equals(firstpart[i])){
                sum1+=(Integer.valueOf(secondpart[i-2]))*(Math.pow(3,(Integer.valueOf(secondpart[i+1]))));
                                 //3                    * 3^2
            }
        i++;
    }

Here you loop with firstpart but use secondpart ‘s value, so it is the problem.