10th Nov - Method Chaining in Java

In Java, method chaining is the chain of methods being called one after another. It is the same as constructor chaining but the only difference is of method and constructor. In this section, we will discuss the method chaining in Java.

Method Chaining

Method chaining is a common syntax to invoke multiple methods calls in OOPs. Each method in chaining returns an object. It violates the need of intermediate variables.

In other words, the method chaining can be defined as if we have an object and we call methods on that object one after another is called method chaining. For example,

obj.method1().method2().method3();

In the above statement, we have an object (obj) and calling method1() then method2(), after that the method3(). So, calling or invoking methods one after another is known as method chaining.

It is also known as parameter idiom or named parameter idiom. Sometimes it is also known as a train wreck because of the increase in the number of methods even though line breaks are often added between methods.

Applications of Method Chaining

• It is used to implement method cascading.
• It is also used to implement in fluent interfaces.

Invoking Methods Without Method Chaining

The following Java program does not implement the method-changing concept.

Product.java

public class Product { private String pname; private int pcost; private int quantity; public void setPname (String pname) { this.pname = pname; } public void setPcost(int pcost) { this.pcost = pcost; } public void setQuantity (int quantity) { this.quantity = quantity; } public void detail() { System.out.println("The product name is " + pname + ". It's cost is " + pcost + ". Available quantity is "+quantity); } public static void main(String args[]) { //creating an object of the Product class Product product = new Product(); //calling methos without using chaining product.setPname("AC"); product.setPcost(20000); product.setQuantity(4); product.detail(); } }

Output:

The product name is AC. It's cost is 20000. Available quantity is 4

Invoking Methods with Method Chaining

Student.java

public class Student { private int id; private String name; private int age; private int std; public Student setId(int id) { this.id = id; //"this" (the current Student object) to allow for further chained method calls return this; } public Student setName(String name) { this.name = name; return this; } public Student setAge(int age) { this.age = age; return this; } public Student setStd(int std) { this.std = std; return this; } public void detail() { System.out.println("Student Detail is:\n"); System.out.println("Id: "+id+ "\nName: "+name+"\nAge: "+age+ "\nStandard: "+std); } public static void main(String args[]) { Student student = new Student(); //method chaining student.setId(1183).setName("Herry Tangri").setAge(17).setStd(9).detail(); } }

Output:

Student Detail is:
Id: 1183
Name: Herry Tangri
Age: 17
Standard: 9

Let's see another example.

DomNumber.java

public class DomNumber { private int number; //creating a constructor DomNumber(int initialNum) { number=initialNum; } public DomNumber add(int toAdd) { number+=toAdd; //returns an instance of DomNumber return this; } //method to print the number public void print() { System.out.println(number); } }

MethodChaining.java

public class MethodChaining { public static void main(String args[]) { DomNumber myNumber = new DomNumber(1); myNumber.add(5).print(); } }

Output:

In the above program, the statement myNumber.add(5).print(); can also be written as follows:

myNumber.add(5) .add(10) .print();

We can also call any number of add() methods.

myNumber.add(5) .add(10) .add(2) .add(20) .print();

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