Question

I’m trying to implement an algorithm in one method that takes in two lists of type studentlist and I need to access the array from the constructor method, studentList to get the size and the student numbers to compare between lists.

e.g.

for (int i = 0; i < L1.studentID.length-1; i++) {
    for (int j = 0; j < L2.studentID.length-1; j++) {
        if (L1.studentID[i] = L2.studentID[j]) {
            num++; }}}

Most of the constructor, and not including the 2nd one for accessing lists in a file instead of randomly generated:

studentID=new int[size];
boolean[] usedID=new boolean[IDrange];
for (int i=0;i<IDrange;i++) usedID[i]=false;
for (int i=0;i<size;i++) {
    int t;
    do {
    t=(int)(Math.random()*IDrange);
    } while (usedID[t]);
    usedID[t]=true;
    studentID[i]=t; }

Size (list.studentID.length or I could have used list.numberOfStudents which is built in) seems fine, but I’m having trouble with getting the elements of the array themselves. I figure I could just do list.studentID[i] but I get a ‘type mismatch: cannot convert from int to boolean’.

Any ideas?

Answer 1

Your issue is here:

if (L1.studentID[i] = L2.studentID[j]) 

You are making an attribution of L2.studentID[j] to L1.studentID[i] and then passing the value of L1.studentID[i] to the if

The if in java expects explicittly a boolean value.

You either want to do:

if (L1.studentID[i] == L2.studentID[j])

or

if ((L1.studentID[i] = L2.studentID[j])!=0)

The code you currently have is the same as doing:

L1.studentID[i] = L2.studentID[j];
if (L1.studentID[i]){  <-- this won't work because L1.studentID[i] is an int and the if expects a boolean
...