How to check null condition for the boolean variable

Question

I have a class as shown

package com;

public class Person {
boolean registered;

public boolean isRegistered() {
    return registered;
}

public void setRegistered(boolean registered) {
    this.registered = registered;
}
}

The Data to Person Object will be set based on the Data present in DB . The problem is that for older records the registered filed is not present .

so i how can i test if the filed is present or not ??

package com;

public class Test {

    public static void main(String args[]) {
        Person per = new Person();

        if (per.isRegistered()) {

        }
    }

}

How can i check if the per.isRegistered() field is present or not for that Person Object ??

You could always just default the registered boolean to false since if the field is not set, you could assume it's not registered. — Supericy
– Supericy, Commented Mar 4, 2013 at 11:35

T.J. Crowder · Accepted Answer · 2013-03-04 11:32:23Z

6

The way your Person class is currently defined, you can't, because boolean (the primitive type) has no null value, only true and false.

You could use Boolean (the object equivalent), which can be null, Boolean.TRUE, or Boolean.FALSE.

But more likely you want to solve this at a deeper level. You've said you have data in your database for which this field isn't present. Are those records considered registered or not? Your class should reflect the answer to that question.

answered Mar 4, 2013 at 11:32

T.J. Crowder

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1 Comment

Marko Topolnik Over a year ago

The way it usually happens in practice, the answer is context-dependent and is not a property of the class. Business logic is usually best done with a clean separation of code and data.

Subhrajyoti Majumder · Accepted Answer · 2013-03-10 07:21:51Z

5

boolean is primitive data type which can not be null, only can be true or false. But Boolean Object which is rapper of boolean data type, It could be null and Boolean.TRUE and Boolean.FALSE;

public class Person {
    Boolean registered;
    ...
}

...

Person per = new Person();

if (per.isRegistered()!=null ) {
    if(!per.isRegistered()){
         ...
    }else{
         ...
    }
}

edited Mar 10, 2013 at 7:21

answered Mar 4, 2013 at 11:33

Subhrajyoti Majumder

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Comments

Grant Thomas · Accepted Answer · 2013-03-04 11:32:40Z

3

boolean can't be null; you'd need to use (Boolean) or construct a composite type.

answered Mar 4, 2013 at 11:32

Grant Thomas

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Comments

pillingworth · Accepted Answer · 2013-03-04 11:33:19Z

1

You need a three state boolean; true, false and not there.

You can achieve this by using Boolean class instead of the primitive boolean and use null as the "not there" indicator.

answered Mar 4, 2013 at 11:33

pillingworth

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Comments

zoom · Accepted Answer · 2013-03-04 11:34:45Z

1

I don't really get what is on your mind. But if you want to handle a boolean whose values can be one of the following {true/false/null}, you should use a Boolean object with is a simple boolean wrapper, but it can take the null value (as every Java Object can be set to null).

answered Mar 4, 2013 at 11:34

zoom

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gd1 · Accepted Answer · 2013-03-04 12:36:15Z

1

You can use the Boolean (capital B) class which allows NULL values for references of its kind.

Alternatively, you can use an enum having three possible values: NOT_AVAILABLE, YES, NO. This has a clearer semantics and allows you to add other possible values later (if needed).

edited Mar 4, 2013 at 12:36

answered Mar 4, 2013 at 11:33

gd1

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Vitaliy Kulikov · Accepted Answer · 2017-12-04 09:38:23Z

1

You should use Optional

if (Optional.ofNullable(per.isRegistered()).orElse(false)) {
  // ...
}

answered Dec 4, 2017 at 9:38

Vitaliy Kulikov

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1 Comment

Vpn_talent Over a year ago

I think this will be very helpful or easy.

triclosan · Accepted Answer · 2013-03-04 11:34:14Z

0

boolean registered as field it's false by default. Moreover boolean not related to Object class but primitive value so can't be null at all.

Only one Null-pointer you may get here it's when per is null

answered Mar 4, 2013 at 11:34

triclosan

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Christian Achilli · Accepted Answer · 2013-03-04 11:34:17Z

0

Make the column nullable and use a Boolean instead of boolean. For the specific problem though, I think you can assume that if it is null the user is not registered.

answered Mar 4, 2013 at 11:34

Christian Achilli

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Thijmen Venus · Accepted Answer · 2013-03-04 11:34:39Z

0

You have to extend the person class to use it in the test class. You also have to define the boolean.

answered Mar 4, 2013 at 11:34

Thijmen Venus

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