Implement One Interface from Another in Java

No, we cannot implement one interface from another you can just extend it using the extends keyword as −

interface ArithmeticCalculations{
   public abstract int addition(int a, int b);
   public abstract int subtraction(int a, int b);
}
interface MathCalculations implements ArithmeticCalculations{
   public abstract double squareRoot(int a);
   public abstract double powerOf(int a, int b);
}

Still, if you try to implement one interface from another using the implements keyword. The compiler does not recognize the implements keyword after the name of the interface and throws a compile time error saying “'{' expected”.

Example

In the following Java program, we have two interfaces namely, ArithmeticCalculations and MathCalculations and, we are trying to implement on interface from the other.

interface ArithmeticCalculations{
   public abstract int addition(int a, int b);
   public abstract int subtraction(int a, int b);
}
interface MathCalculations implements ArithmeticCalculations{
   public abstract double squareRoot(int a);
   public abstract double powerOf(int a, int b);
}

Compile time error

On compiling, the above program generates the following compile time error −

Output

MathCalculations.java:8: error: '{' expected
interface MathCalculations implements ArithmeticCalculations{
^
1 error

If you compile the same program using eclipse it gives you a compile time error suggesting that “extends keyword is expected instead of implements”.