Uninitialized Object vs Object Initialized to NULL

JavaNullInitialization

Java Problem Overview


I'm working in Java.

I commonly setup some objects as such:

public class Foo {
    private SomeObject someName;

    // do stuff

    public void someMethod() {
        if (this.someName != null) {
            // do some stuff
        }
    }
}

The question is: Is someName in this example equated to null, as-in I can reliably for all objects assume null-checking uninitialized objects will be accurate?

Java Solutions


Solution 1 - Java

Correct, both static and instance members of reference type not explicitly initialized are set to null by Java. The same rule applies to array members.

From the Java Language Specification, section 4.12.5:

> Initial Values of Variables

> Every variable in a program must have a value before its value is used:

> Each class variable, instance variable, or array component is initialized with a default value when it is created

> [...] For all reference types, the default value is null.

Note that the above rule excludes local variables: they must be initialized explicitly, otherwise the program will not compile.

Solution 2 - Java

If an Object reference has been declared but not instantiated, its value is null.

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Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionSnakeDocView Question on Stackoverflow
Solution 1 - JavaSergey KalinichenkoView Answer on Stackoverflow
Solution 2 - JavaJared NielsenView Answer on Stackoverflow