The definition itself is very clear and proxy pattern is used when we want to provide controlled access of a functionality. Proxy pattern intent is to “Provide a surrogate or placeholder for another object to control access to it”. Check out Composite Pattern article for different component of composite pattern and example program. Here drawing is made up of different parts and they all have the same operations. Let’s understand it with a real-life example – A diagram is a structure that consists of Objects such as Circle, Lines, Triangle, etc and when we fill the drawing with color (say Red), the same color also gets applied to the Objects in the drawing. When we need to create a structure in a way that the objects in the structure have to be treated the same way, we can apply the composite design pattern. Check out Adapter Pattern for example program and it’s usage in Java.Ĭomposite pattern is one of the Structural design patterns and is used when we have to represent a part-whole hierarchy. So the mobile charger works as an adapter between the mobile charging socket and the wall socket. As a real-life example, we can think of a mobile charger as an adapter because the mobile battery needs 3 volts to charge but the normal socket produces either 120V (US) or 240V (India). The object that joins these unrelated interfaces is called an Adapter. The adapter design pattern is one of the structural design patterns and it’s used so that two unrelated interfaces can work together. Structural patterns provide different ways to create a class structure, for example using inheritance and composition to create a large object from small objects. Check out Prototype Pattern for sample program. However whether to use the shallow or deep copy of the Object properties depends on the requirements and it’s a design decision. It should not be done by any other class. Prototype design pattern mandates that the Object which you are copying should provide the copying feature. This pattern uses java cloning to copy the object. So this pattern provides a mechanism to copy the original object to a new object and then modify it according to our needs. The prototype pattern is used when the Object creation is a costly affair and requires a lot of time and resources and you have a similar object already existing.
Check out Builder Pattern for example program and classes used in JDK.< Builder pattern solves the issue with a large number of optional parameters and inconsistent state by providing a way to build the object step-by-step and provide a method that will actually return the final Object. This pattern was introduced to solve some of the problems with Factory and Abstract Factory design patterns when the Object contains a lot of attributes.
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Check out Abstract Factory Pattern to know how to implement this pattern with example program. In Abstract Factory pattern, we get rid of if-else block and have a factory class for each sub-class and then an Abstract Factory class that will return the sub-class based on the input factory class. If you are familiar with the factory design pattern in java, you will notice that we have a single Factory class that returns the different sub-classes based on the input provided and the factory class uses if-else or switch statements to achieve this. This is one of the most widely used java design patterns.Ībstract Factory pattern is similar to Factory pattern and it’s a factory of factories. Check out Factory Design Pattern for example program and factory pattern benefits. We can apply a Singleton pattern on the Factory class or make the factory method static. This pattern takes out the responsibility of the instantiation of a class from the client program to the factory class. The factory design pattern is used when we have a superclass with multiple sub-classes and based on input, we need to return one of the sub-class. This is one of the most discussed java design patterns. Check out Singleton Design Pattern to learn about different ways to implement Singleton pattern and pros and cons of each of the method. The implementation of the Singleton pattern has always been a controversial topic among developers. It seems to be a very simple design pattern but when it comes to implementation, it comes with a lot of implementation concerns. Singleton pattern restricts the instantiation of a class and ensures that only one instance of the class exists in the Java virtual machine. Creational design patterns provide solution to instantiate a object in the best possible way for specific situations.
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