Implementation based on test Java (bytewise) JUnit test-CodePudding

I'm trying to implement a class in order to pass the following test (Using bytewise operators & and |

public void hasFlagTest1() {
    byte resource = ResourceUtil.getFlag(FLAG_PUBLIC_SECURITY, FLAG_PRIVATE_SECURITY, FLAG_BASIC_LIFE_SUPPORT);

    Assert.assertTrue(ResourceUtil.hasPublicSecurity(resource));
    Assert.assertTrue(ResourceUtil.hasPrivateSecurity(resource));
    Assert.assertTrue(ResourceUtil.hasBasicLifeSupport(resource));
    Assert.assertFalse(ResourceUtil.hasVolunteers(resource));
    Assert.assertFalse(ResourceUtil.hasAllOpts(resource));
}

The constant values that are passed by parameters are

public static final byte FLAG_PRIVATE_SECURITY = 1;
public static final byte FLAG_PUBLIC_SECURITY = 2;
public static final byte FLAG_BASIC_LIFE_SUPPORT = 4;
public static final byte FLAG_VOLUNTEERS = 8;
public static final byte FLAG_ALL_OPTS  = 15;

I have already created a class but not sure how to implement all methods in order to make this test pass, here's the class:

public class ResourceUtil {

public static byte getFlag(byte arg, byte arg2, byte arg3){
    
    return result;  //just a value, not implemented
}; 

public static boolean hasPublicSecurity(byte resource) {

    return true;  //just a value, not implemented
}

public static boolean hasPrivateSecurity(byte resource) {

    return true;  //just a value, not implemented
}

public static boolean hasBasicLifeSupport(byte resource) {

    return true;  //just a value, not implemented
}

public static boolean hasVolunteers(byte resource) {
    return true;  //just a value, not implemented
}

public static boolean hasAllOpts(byte resource) {

    return true;  //just a value, not implemented
}

}

Any idea? I've been trying some

CodePudding user response：

It looks like you are just looking for set bits inside a byte (and for all set bits in that last method). To do this you can simply use your flags as a mask and compare to the flag.

public class ResourceUtil {

    public static boolean hasPublicSecurity(byte resource) {
        return resource & FLAG_PUBLIC_SECURITY == FLAG_PUBLIC_SECURITY;
    }

    public static boolean hasPrivateSecurity(byte resource) {
        return resource & FLAG_PRIVATE_SECURITY == FLAG_PRIVATE_SECURITY;
    }

    public static boolean hasBasicLifeSupport(byte resource) {
        return resource & FLAG_BASIC_LIFE_SUPPORT == FLAG_BASIC_LIFE_SUPPORT;
    }

    public static boolean hasVolunteers(byte resource) {
        return resource & FLAG_VOLUNTEERS == FLAG_VOLUNTEERS;
    }

    public static boolean hasAllOpts(byte resource) {
        return resource & FLAG_ALL_OPTS == FLAG_ALL_OPTS;
    }

}

NOTE: It's not completely clear to me what the getFlags method is supposed to accomplish, but these checks should work

CodePudding user response：

The best (and probably fastest in terms of performance) way to do it would be to create a logical AND operation between the resources that you receive and the location of the bit.

So something like this:

public static boolean hasPublicSecurity(byte resource) {
    return (resource & FLAG_PUBLIC_SECURITY) == FLAG_PUBLIC_SECURITY;
}

public static boolean hasPrivateSecurity(byte resource) {
    return (resource & FLAG_PRIVATE_SECURITY) = FLAG_PRIVATE_SECURITY;
}

public static boolean hasBasicLifeSupport(byte resource) {
    return (resource & FLAG_BASIC_LIFE_SUPPORT) == FLAG_BASIC_LIFE_SUPPORT;
}

public static boolean hasVolunteers(byte resource) {
    return (resource & FLAG_VOLUNTEERS) == FLAG_VOLUNTEERS;
}

public static boolean hasAllOpts(byte resource) {
    return (resource & FLAG_ALL_OPTS) == FLAG_ALL_OPTS;
}

The reason for the code is as follows, let's assume in your example that we have the value 7 (111 in binary), when we check for PUBLIC_SECURITY we're basically checking if:

111 & 001 == 001

If the result is zero, that means that the relevant bit was not 1.