Java.Java8.DoubleUnaryOperator, IntUnaryOperator, and LongUnaryOperator?

✅ What do they have in common?

They are all specialized versions of UnaryOperator<T> for Java primitives: double, int, and long.

To avoid autoboxing and unboxing, which happens with generic types like UnaryOperator<Integer> → it’s slower and memory-intensive.

@FunctionalInterface
public interface DoubleUnaryOperator {
    double applyAsDouble(double operand);
}

➤ Example:

DoubleUnaryOperator half = d -> d / 2.0;
System.out.println(half.applyAsDouble(10.0)); // 5.0

@FunctionalInterface
public interface IntUnaryOperator {
    int applyAsInt(int operand);
}

➤ Example:

IntUnaryOperator increment = i -> i + 1;
System.out.println(increment.applyAsInt(9)); // 10

@FunctionalInterface
public interface LongUnaryOperator {
    long applyAsLong(long operand);
}

➤ Example:

LongUnaryOperator doubleIt = l -> l * 2;
System.out.println(doubleIt.applyAsLong(10000000000L)); // 20000000000

Interface	Input Type	Output Type	Method	Avoids Boxing?
`UnaryOperator<T>`	T	T	`apply(T t)`	❌ No
`DoubleUnaryOperator`	`double`	`double`	`applyAsDouble()`	✅ Yes
`IntUnaryOperator`	`int`	`int`	`applyAsInt()`	✅ Yes
`LongUnaryOperator`	`long`	`long`	`applyAsLong()`	✅ Yes