for loop

import java.util.List;
import java.util.Vector;

class HandshakeCalculator {

    List < Signal > calculateHandshake(int number) {

        final List < Signal > output = new Vector < Signal > ();
        int action = 0, action_incr = 1, end = Signal.values().length;

        if ((number & 16) != 0) {
            action = 3;
            action_incr = -1;
            end = -1;
        }

        for (; action != end; action += action_incr)
            if ((number & (1 << action)) != 0)
                output.add(Signal.values()[action]);

        return output;
    }
}

This approach starts by importing from packages for what will be needed.

In the calculateHandshake() method, a final List is defined to hold the signals. It is final because it does not need to be reassigned after it is created.

A series of variables are defined and initialized for normal looping through the Signal values collection. Normal looping would start at index 0 and proceed by adding 1 to the index up to but not including the length of the Signal values collection.

The number is then compared with 16 by using the bitwise AND operator.

For example, given the bitwise value is 16 (binary 10000) and the input is 24 (binary 11000), then ANDing 10000 with 11000 results in 10000, which is not 0, so the number contains bitwise16.

Given the bitwise value is 16 (binary 10000) and the input is 8 (binary 01000), then ANDing 10000 with 01000 results in 00000, which is 0, so the number does not contain bitwise16.

If the number contains bitwise 16, then the looping variables are set to iterate in reverse.

The for loop is set up with the looping variables.

In the body of the for loop, the left shift operator is used to shift 1 to the left for the number of places of the value of the action variable. (The action variable is for the index in the Signals values collection.) The bitwise AND operator is used to compare the bitwise value of the Signals index with the number.

For example, if the index is 2 (binary 010) and the input is 6 (binary 110), then ANDing 010 with 110 results in 010, which is not 0, so the input contains bitwise2.

If the index value is 2 (binary 010) and the input is 4 (binary 100), then ANDing 010 with 100 results in 000, which is 0, so the input does not contain bitwise 2.

If the number contains the bitwise value of the index, then the Signal value at that index is added to the List.

After the for loop is done, the List is returned from calculateHandshake().