Reshma Bidikar

In this blog post, I will be explaining how the Java 8 functional interface BiFunction works. To know more about functional interfaces, you can refer this blog post.

The BiFunction is a specialization of the Function interface that accepts 2 arguments. Just like Function it provides a method called apply. This method accepts 2 arguments of any data type and returns a result. So it basically applies the logic in the apply method to the input parameters and returns the result.

BiFunction Interface Example with two integer inputs and Integer output

Consider the following code snippet:

private static void example1()
 { 
 BiFunction<Integer,Integer,Integer> multiplier = (a,b) -> {return a\*b;}; int input1 = 6; 
 int input2 = 8; 
 System.out.println("Result of multiplying "+input1+" and "+input2 +" is "+multiplier.apply(input1,input2) ); 
 }

Here, we have written a BiFunction implementation that accepts 2 integer values, multiplies them and returns the result. The BiFunction.apply method is implemented using a lambda expression. This expression accepts two integer values, multiplies them and returns the result. So when you execute this code, it will print the following output:

Result of multiplying 6 and 8 is 48

BiFunction Interface Example with String and Character input and String array as the output

Consider the following code snippet:

private static void example2(){ 
String input = "hello,world"; BiFunction<String,Character,String[]> stringSplitter = (inputStr,inputChar) -> {String[] list = inputStr.split(inputChar.toString()); 
return list;
}; 
String[] result = stringSplitter.apply(input, new Character(',')); 
for(String str:result) { 
System.out.println("String is "+str); 
} 
}

This code splits a String into a String array based on the character specified. It returns the String array. So when this code is executed, it will print the following output:

String is hello
String is world

BiFunction Interface Example with a String and Integer as input and Object as output

Consider the following code snippet:

public class Person {

private String name; private int age;

public Person(String name, int age) { super(); this.name = name; this.age = age; }

// Getter setter methods

}

private static void example3(){ String input = "hello,world";

BiFunction<String,Integer,Person> personCreator = (name,age) -> {return new Person(name,age);}; Person person = personCreator.apply("Mickey Mouse",35); System.out.println("Person object created with name as "+person.getName()); }

This BiFunction implementation accepts a String and Integer as input, creates a Person object with those values and returns that Person object. So when you execute this code, it will print the following output:

Person object created with name as Mickey Mouse

You can get the source code for this example along with other code for other Java 8 examples at the Github repository here.