JAVA

functional interface java

A functional interface is an interface that contains only one abstract method. They can have only one functionality to exhibit.

creating the functional interface in java

package com.concretepage;

@FunctionalInterface
public interface Calculator {
   long calculate(long num1, long num2);
} 

how to declare a interface in java

// Assume we have the simple interface:
interface Appendable {
	void append(string content);
}
// We can implement it like that:
class SimplePrinter implements Appendable {
 	public void append(string content) {
   		System.out.println(content); 
    }
}
// ... and maybe like that:
class FileWriter implements Appendable {
 	public void append(string content) {
   		// Appends content into a file 
    }
}
// Both classes are Appendable.
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how to implement a interface in java

java define interface

/* File name : Animal.java */
interface Animal {
   public void eat();
   public void travel();
}