What's the Key Difference Between Java's `&` and `&&` Operators?

Understanding the Distinction Between '&' and '&&' in Java

In Java, the '&' operator has traditionally been associated with bitwise operations on integers. However, it recently emerged that this operator can also perform boolean operations, bringing it into question with the '&&' operator.

While both '&' and '&&' verify the truthfulness of boolean operands, they differ in their evaluation logic. '&&' performs a lazy evaluation, meaning it only evaluates the right-hand side (RHS) operand if the left-hand side (LHS) operand is true. This ensures that if the LHS operand is false, the RHS operand is not evaluated, potentially avoiding unnecessary computation and preventing exceptions from occurring.

In contrast, '&' relentlessly evaluates both operands. This can lead to exceptions if the RHS operand is not well-defined for certain LHS operand values. Consider the example:

if ((x != 0) & (1/x > 1)) {
    // ...
}

If 'x' is 0, this expression will throw an exception when attempting to evaluate '1/x'. To prevent this, use '&&' instead:

if ((x != 0) && (1/x > 1)) {
    // ...
}

Here, it will only proceed to evaluate '1/x' if 'x' is not 0, thus avoiding the exception.

Furthermore, the '|', '|>' counterparts of the boolean operators behave similarly. '|>' stops evaluating if the first operand evaluates to true since the result will always be true.

Understanding this subtle distinction between '&' and '&&' is crucial for writing efficient and robust Java code that avoids runtime errors caused by premature evaluation.

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