Should Static Classes Be Inner?

Do inner classes have to be static?

Inner Classes As with instance methods and variables, an inner class is associated with an instance of its enclosing class and has direct access to that object’s methods and fields.

Also, because an inner class is associated with an instance, it cannot define any static members itself..

Can inner class final?

Inner class are defined inside the body of another class (known as outer class). These classes can have access modifier or even can be marked as abstract and final. Inner classes have special relationship with outer class instances.

Is StringBuilder thread safe?

StringBuilder is not synchronized so that it is not thread-safe. By not being synchronized, the performance of StringBuilder can be better than StringBuffer. If we are working in a single-threaded environment, using StringBuilder instead of StringBuffer may result in increased performance.

Can static member classes contain non static methods?

A static class has no pointer to its outer class and can therefore only refer to static fields and methods of the outer class. A static class may however itself contain non-static methods. There’s no such thing as a “static class” in Java (at least not in the way you seem to understand it).

What is a static inner class?

A static inner class is a nested class which is a static member of the outer class. It can be accessed without instantiating the outer class, using other static members. Just like static members, a static nested class does not have access to the instance variables and methods of the outer class.

Should static classes be avoided?

General rule – don’t use static classes unless… There is no other way to do it (to write your code). Having a god (static class) is not bad, but when you talk with him, make sure that no one can disturb you! (take care of singleton pattern issues, because static class is just a singleton).

Is static inner class thread safe?

static methods and inner classes don’t have any access to the variables of their dynamic counter part, and consequently can’t use monitors/synchronize on an instance of their parent class. Of course this doesn’t mean that declaring them and using them is inherently non-thread safe.

Can Java inner class be static?

Static nested classes i.e., an object of the inner class is always strongly associated with an outer class object. But in the case of static nested class, Without an outer class object existing, there may be a static nested class object.

Why is static inner class singleton thread safe?

So, Bill Pugh suggested a concept of inner static classes to use for singleton. When the singleton class is loaded, inner class is not loaded and hence doesn’t create object when loading the class. Inner class is created only when getInstance() method is called.

Is HashMap thread safe?

HashMap is non synchronized. It is not-thread safe and can’t be shared between many threads without proper synchronization code whereas Hashtable is synchronized. It is thread-safe and can be shared with many threads.

Can inner class have constructor?

Every Object (without any exceptions) is created by invoking a constructor. Here you can see that the compiler implements your inner class by declaring a final field member holding a reference to the enclosing class. … You can, though, do constructor chaining between other declared constructors of your inner class.

How do you access static class?

You cannot create an object of the static class; therefore the members of the static class can be accessed directly using a class name like ClassName.