Can interfaces have constructors in Java?

No, interfaces can't have constructors for the following reasons −

• All the members of an interface are abstract, and since a constructor cannot be abstract.

Still, if you try to write a constructor within an interface it will generate a compile time error.

Example

public interface InterfaceTest {
   InterfaceTest(){
   }
   public abstract void display();
   public abstract void show();
}

Error

C:\Sample>javac InterfaceTest.java
InterfaceTest.java:2: error: <dentifier> expected
public InterfaceTest(){
                     ^
1 error