[hardwired]

You must provide the method declaration for each method defined in the implemented interface. What you do in the method body is up to you.
In pseudo code:

Code:

public interface Mapper {
    public void createSchema();
    public int getNoOfClasses();
    public void setHost(String hostName);
}

class NeedAllMethods implements Mapper {
    public void createSchema() {
        // implementation...
    }

    public int getNoOfClasses() {
        // implementation...
        return intValue;
    }

    public void setHost(String hostName) {
        // implementation...
    }
}

class NeedOnlyOne implements Mapper {
    public void createSchema() {
        // no-op okay
    }

    public int getNoOfClasses() {
        // no-op okay but you must
        // return an int value.
        return 0;
    }

    public void setHost(String hostName) {
        // no-op okay
    }
}