Question: Is Static Inner Class Thread Safe?

How do you access a static inner class?

And like static class methods, a static nested class cannot refer directly to instance variables or methods defined in its enclosing class: it can use them only through an object reference.

They are accessed using the enclosing class name.

To instantiate an inner class, you must first instantiate the outer class..

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).

Is static class thread safe?

2 Answers. No, it doesn’t say that static classes are thread safe, it says that public static members are thread safe. For static methods for example, this means that they only use the data that you send in as parameters, or other static members that are also thread safe.

Should static classes be inner?

That means it can be instantiated outside the scope of an outer class object. It also means that if you ‘export’ an instance of the inner class, it will not prevent the current object to be collected. As a basic rule, if the inner class has no reason to access the outer one, you should make it static by default.

Can we override static method?

Can we Override static methods in java? We can declare static methods with the same signature in the subclass, but it is not considered overriding as there won’t be any run-time polymorphism. Hence the answer is ‘No’.

Is it possible to start a thread twice?

After starting a thread, it can never be started again. … If you does so, an IllegalThreadStateException is thrown. In such case, thread will run once but for second time, it will throw exception.

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.

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.

What happens when two threads access Singleton at the same time?

Now coming to your question: if you share your singleton object among multiple threads and access it concurrently, every single thread will execute Singleton object’s portion of code, wrapped in its own execution. Also if you write a Thread.

Which is faster HashMap or ConcurrentHashMap?

If you choose a single thread access use HashMap , it is simply faster. For add method it is even as much as 3x more efficient. Only get is faster on ConcurrentHashMap , but not much. When operating on ConcurrentHashMap with many threads it is similarly effective to operating on separate HashMaps for each thread.

Are Arraylists thread safe?

ArrayList , on the other hand, is unsynchronized, making them, therefore, not thread safe. With that difference in mind, using synchronization will incur a performance hit. So if you don’t need a thread-safe collection, use the ArrayList .

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.

Can we create a static class in Java?

The answer is YES, we can have static class in java. In java, we have static instance variables as well as static methods and also static block. Classes can also be made static in Java. In java, we can’t make Top-level (outer) class static.

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.

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.

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.

Is singleton thread safe in spring?

Spring singleton beans are NOT thread-safe just because Spring instantiates them. Sorry. Spring just manage the life cycle of singleton bean and maintains single instance of object. Thread safety has nothing to do with it.

Can we make a class private?

No, we cannot declare a top-level class as private or protected. It can be either public or default (no modifier). If it does not have a modifier, it is supposed to have a default access.