Why Does the Ternary Operator Allow Null While the If Statement Does Not?

NullPointerException in Java: Ternary Operator vs. If Statement

Consider the following Java code snippet:

<code class="java">public class Main {

    private int temp() {
        return true ? null : 0; // No compiler error
    }

    private int same() {
        if (true) {
            return null; // Compile-time error
        } else {
            return 0;
        }
    }

    public static void main(String[] args) {
        Main m = new Main();
        System.out.println(m.temp());
        System.out.println(m.same());
    }
}</code>

Question: Why does the temp() method (using a ternary operator) not produce a compiler error, while the same() method (using an if statement) does?

Answer: The Java compiler interprets null as a null reference to an Integer. When using the conditional operator, autoboxing/unboxing rules are applied (as per the Java Language Specification, 15.25). This allows the compiler to proceed without issuing an error, even though a NullPointerException will be thrown at run time.

In contrast, when using an if statement, the compiler applies standard type checking rules. Since null is not a valid int value, a compile-time error is produced.

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