is it right when i want to view some maximum value from database MySql using Java Netbeans

public Double maksimal1() {
    double m1 = 0;
    query = "SELECT MAX(`K1`) FROM penilaian ";
    status = koneksi.eksekusiQuery(query, true);
    if(status){
        rsMatriks = koneksi.getRs();
        try{
            rsMatriks.next();
            m1= rsMatriks.getDouble("K1");
            rsMatriks.close();
        }catch(SQLException ex){
            return null;
        }
    }
    return m1;
}

Your query returns 1 column which you should alias as K1 if you want to access it by name:

query = "SELECT MAX(`K1`) AS K1 FROM penilaian";

or if you want to access it by its index which is 1 since it is the only column:

m1 = rsMatriks.getDouble(1);