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Programmers frequently make errors regarding the precedence of operators because of the unintuitively low precedence levels of &, |, ^, <<, and >>. Avoid mistakes regarding precedence through the suitable use of parentheses, which also improves code readability. The precedence of operations by the order of the subclauses are is defined in the Java Tutorials [Tutorials 20082013].

Although it advises against depending on parentheses for specifying evaluation order, EXP05-J. Do not write more than once to the same variable within an expression applies only to expressions that contain side effects.

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public class TestPrintValue {
    public static void main(String[] args) {
        String s = null;
    // Prints "1"
    System.out.println("value=" + s == null ? 0 : 1); // Prints "1"
    }
}

However, the precedence rules result in the expression to be printed being parsed as ("value=" + s) == null ? 0 : 1.

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public class PrintValue Test{
    public static void main(String[] args) {
    String     String s = null;
    // Prints "value=0" as expected
   System System.out.println("value=" + (s == null ? 0 : 1)); // Prints "value=0" as expected
    }
}

Applicability

Mistakes regarding precedence guidelines can cause an expression to be evaluated in an unintended way, which can lead to unexpected and abnormal program behavior.

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Detection of all expressions using low-precedence operators without parentheses is straightforward. Determining the correctness of such uses is infeasible in the general case; , although heuristic warnings could be useful.

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