Is it possible to perform an assignment and comparison in if clauses in Java?

Question

It is possible to assign and at the same time perform a comparison in an if clause in Java?

For example:

String linha = leitor.readLine();
String saida = "";
if (linha = leitor.readLine()) {
    saida += "\n";
}

That doesn’t seem to work.

As I would?

Answer 1

It does not work directly because java does not allow automatic conversion to boolean. But you can do the following:

String linha = leitor.readLine();
String saida = "";
if ( (linha = leitor.readLine()) != null) {
    saida += "\n";
}

Just as in C and C++, the assignment is an expression, whose value is that of the variable that has just been assigned. In this case its type is String, what is not accepted within a if. With the set of parentheses, we can isolate the value of the assignment and compare it with null to find out if the operation occurred as expected.

Answer 2

You don’t show what condition you want to test on if, let’s call it condicao:

if ((linha = leitor.readLine()) == condicao) {
    saida += "\n";
}

The code above will first assign the linha the value of readLine and then make the comparison with the condicao.