Interface with static and non-static method in java

Question

I am practicing the strategy pattern and trying to apply the code here. https://www.tutorialspoint.com/design_pattern/strategy_pattern.htm

What I am confusing is I did not declare any static method in the Context class as it showed that cannot do such the operation as I made a static reference to the non-static reference method.

I want to know why is this happening. Any help is highly appreciated.

Here is part of my interface and relevant code.

interface ArithmeticStratrgy
{
public int doOperation(int num1, int num2);
}

class AddOperateion implements ArithmeticStratrgy 
{
@Override
public int doOperation(int num1, int num2) {
    return num1 + num2;
    }
}

class Context 
{
private ArithmeticStratrgy strategy;

public Context(ArithmeticStratrgy strategy) {
    this.strategy = strategy;
    }

public int executeArithmeticStrategy(int num1, int num2) {
    // Cannot make a static reference to the non-static method 
    // doOperation(int, int) from the type ArithmeticStratrgy
    return ArithmeticStratrgy.doOperation(num1, num2);
    }
}