Single value computation
First of all it is always helpful to format your code properly (I now used the default code convention for Java):

int inputarray={3,5,2,6,7};
int inputlength=inputarray.length;
while (inputlength != 0) {  
    for (int i = 0; i &lt; inputlength-1; i++) {
        inputarray[i] = inputarray[i+1] + inputarray[i];      
    }
    inputlength--;
}
System.out.println(inputarray[0]);


Also it is better to test for inputlength &lt; 0 because then the termination of the loop is much more likely...

For performance tuning:

Try to create a formula for your problem to calculate the result. Your example could be reduced to 3 + 4*5 + 6*2 + 4*6 + 7...

Find a formula such like Gauss did for summing up the parts...