Read Only Interfaces in Java

In Java, a read-only interface is an interface that only declares methods and does not contain any method implementations. These methods are meant to be implemented by a class that implements the interface. A read-only interface can be useful when you want to specify a set of methods that must be implemented by a class, but you don't want to provide any implementation for these methods.

Here is an example of a read-only interface in Java:

public interface ReadOnly {
   int getValue();
}

This interface declares a single method getValue(), which returns an int value. A class that implements this interface must provide an implementation for this method.

Here is an example of a class that implements the ReadOnly interface:

public class ReadOnlyImpl implements ReadOnly {
   private int value;

   public ReadOnlyImpl(int value) {
      this.value = value;
   }

   @Override
   public int getValue() {
      return value;
   }
}

The ReadOnlyImpl class implements the getValue() method of the ReadOnly interface. This class can be used as follows:

ReadOnly ro = new ReadOnlyImpl(10);
int val = ro.getValue(); // val will be 10

In this example, the ReadOnly interface serves as a contract that specifies that a class must implement the getValue() method. The ReadOnlyImpl class satisfies this contract by providing an implementation for the getValue() method.