[java design pattern] strategy pattern

Step 1: Define the interface

public interface ICalculator {
  public int calculate(String exp);
}

Step 2: Define an abstract class (optional, for assistance)

public abstract class AbstractCalculator {
   
	  public int[] split(String exp,String opt){  
	        String array[] = exp.split(opt);  
	        int arrayInt[] = new int[2];  
	        arrayInt[0] = Integer.parseInt(array[0]);  
	        arrayInt[1] = Integer.parseInt(array[1]);  
	        return arrayInt;  
	    }  
}

Step 3: Define the implementation class, inherit the abstract class, and implement the interface

public class Minus extends AbstractCalculator implements ICalculator{

	@Override
	public int calculate(String exp) {
		int[] arrayInt=split(exp,"-");
		return arrayInt[0]-arrayInt[1];
	}

}

Step 4: Test

public class StrategyTest {
    public static void main(String[] args) {
		String exp="2+8";
		ICalculator cal=new Plus();
		int result=cal.calculate(exp);
		System.out.println("2+8="+result);
	}
}