Java – three parameter operators: local variables may not have been initialized

I have the following code

import java.util.Random;

public class ThreeArgumentOperator {

    private static final Random RANDOM = new Random();

    public static void main(String[] args) {
        String test;
        System.out.println(test = getValue() == null ? "" : test);
    }

    public static String getValue() {
        if (RANDOM.nextBoolean()) {
            return "";
        } else {
            return null;
        }
    }

}

The eclipse compiler (I'm using Juno) reports the following errors:

My question is: in this case, should the compiler report that it cannot convert Boolean to string? I understand that the operator = = takes precedence over =, so the compiler should complain about conversion, but that there may be no initialization value

When I change the following lines

System. out. println(test = getValue()== null？ “”：test);

to

System. out. println((test = getValue())== null？ “”：test);

business as usual.

Editor: I also try to compile it directly using javac It gives the same error

error: variable test might not have been initialized
System.out.println(test = getValue() == null ? "" : test);

Solution

The error provided by the compiler is correct According to the operator priority, first evaluate = =, then your ternary operator?: This means that the logic flow is as follows:

getValue() == null

To continue, we assume that the result is wrong The next expression is as follows:

false ? "" : test

The result is a test And our final expression

test = test

But the test was never initialized, so an error occurred