In this program, we defined the interface named MyInterface as a functional interface by writing the annotation above the interface definition. Multiple non-overriding abstract methods found in interface MyInterface Test.java:1: error: Unexpected is not a functional interface If by mistake, we define two abstract methods in the interface, then the compiler would not throw an error or warning because the compiler simply doesn’t know that we want to make the interface as a functional interface, as shown below. Functional interface is an interface which has only one abstract method. Suppose we want to define a functional interface (We read about functional interface in Lambda Expressions). This means that the compiler understands the information provided by an annotation in a program.Ĭomments start with // whereas annotations start with see an example of an annotation. The major difference between comments and annotations is that comments are used to give information about the code for the programmer or someone reading the code to understand, whereas annotations are used to give detailed information about the code for the compiler to understand.

In fact, both are not part of the program itself. Then what is the difference between comments and annotations?īoth comments and annotations are just used to give information about a program and don't interfere with the working of the program. They are also used to give information about the different parts of a program. Comments are written in a program to give information about the different parts of the program so that a person can understand what the program does by reading the comments. Java Annotations are used to add additional information about our program.

Java annotations example