Coding Pattern for use instance member

Suppose i have a class called CommandLineOperation. This class accesses api resources. Thus i have defined one instance member of type APIAccessor.

class CommandLineOperation {
    APIAccessor apiAccessor;
    void create() {
        apiAccessor = new APIAccessor(email,password);
        //do work for creation
    }
    void update() {
        apiAccessor = new APIAccessor(email,password);
        //do work for update
    }
}

class APIAccessor {
    String email;
    String password;
    APIAccessor(email,password) {
        this.email = email;
        this.password = password;
    }
}

The operations in CommandLine, are infrequent, is it a better approach to instantiate APIAccessor under every operations or create once using constructor of CommandLineOperation class. e.g.

CommandLineOperation(String email,String password) {
    this.apiAccessor = new APIAccessor(email,password);
}

Please let me know or suggest good coding design pattern. Or suggest me any reference book so that i can improve my coding standard based on the analysis. Thanks in advance.