Does java have a clamp function?

Ported from a .NET answer:

public static <T extends Comparable<T>> T clamp(T val, T min, T max) {
    if (val.compareTo(min) < 0) return min;
    else if (val.compareTo(max) > 0) return max;
    else return val;
}

Caution: Unlike .NET, primitive types are not allowed in generics, which means they must be boxed/unboxed. When working with primitive types, such as int and double, this implementation will perform three box operations and one unbox operation.

Note: since it’s a port of the .NET answer, I made this a community wiki post.

Is there any built in function for clamping to a range?

No.

Guava includes Ints.constrainToRange() (and equivalent methods for the other primitives). From the release notes:

added constrainToRange([type] value, [type] min, [type] max) methods which constrain the given value to the closed range defined by the min and max values. They return the value itself if it's within the range, the min if it's below the range and the max if it's above the range.

Having looked at the generic clamp method offered up in another answer, it is worth noting that this has boxing/unboxing considerations for primitive types.

public static <T extends Comparable<T>> T clamp(T val, T min, T max) {...}

float clampedValue = clamp(value, 0f, 1f);

This will use the Float wrapper class, resulting in 3 box operations, one for each parameter, and 1 unbox operation for the returned type.

To avoid this, I would just stick to writing it long hand or use a non-generic function for the type you want:

public static float clamp(float val, float min, float max) {
    return Math.max(min, Math.min(max, val));
}

Then just overload with identical methods for every primitive type you require.