Why anonymous class in java

How used and advantage both are different thing , and i alsilo asked how it improve performance. Faizan stackoverflow. Add a comment. Active Oldest Votes. What does this mean? Why use an anonymous class? The Syntax for Anonymous Class Definitions This example demonstrates an anonymous class definition for a comparator that is passed to the sort method in the Collections class. An anonymous class must implement all the abstract methods in the super class or the interface. Improve this answer.

Martin Fink 1, 1 1 gold badge 16 16 silver badges 29 29 bronze badges. Mehraj Malik Mehraj Malik At least part of this is copied verbatim from other sources. Its syntax is:. Note: Anonymous classes are defined inside an expression. So, the semicolon is used at the end of anonymous classes to indicate the end of the expression. In the above example, we have created a class Polygon. It has a single method display. We then created an anonymous class that extends the class Polygon and overrides the display method.

When we run the program, an object p1 of the anonymous class is created. The object then calls the display method of the anonymous class. In the above example, we have created an anonymous class that implements the Polygon interface. In anonymous classes, objects are created whenever they are required. That is, objects are created to perform some specific tasks.

For example,. As mentioned previously, an anonymous class is an expression. The syntax of an anonymous class expression is like the invocation of a constructor, except that there is a class definition contained in a block of code.

The name of an interface to implement or a class to extend. In this example, the anonymous class is implementing the interface HelloWorld. Parentheses that contain the arguments to a constructor, just like a normal class instance creation expression. Note : When you implement an interface, there is no constructor, so you use an empty pair of parentheses, as in this example. A body, which is a class declaration body. More specifically, in the body, method declarations are allowed but statements are not.

Because an anonymous class definition is an expression, it must be part of a statement. In this example, the anonymous class expression is part of the statement that instantiates the frenchGreeting object.

This explains why there is a semicolon after the closing brace. Like local classes, anonymous classes can capture variables ; they have the same access to local variables of the enclosing scope:. An anonymous class cannot access local variables in its enclosing scope that are not declared as final or effectively final.

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