从不同类的另一个构造函数分配默认构造函数值

Question

I need to assign default values stored in my first class constructor to second class constructor following shows my second class from where i am calling Guest class constructors default value.

public class AuditoriumSeating {
   Guest[][] seating;

   public AuditoriumSeating(int rowNum, int columnNum) {
      seating = new Guest[rowNum][columnNum];
      Guest c;
      for ( int i=0; i < rowNum; i++ ) {
         for( int j=0; j < columnNum; j++ ) {
            seating[i][j] = ;   
         }
      }
   }
}

But the problem is I can not figure out what to assign seating[i][j] with, so I can assign this array seating[][] with a default constructor value that I have assigned in my previous class constructor. Here is my guest class constructor:

public class Guest {

   public String lastName;
   public String firstName;

   public Guest()
   {
      firstName="???";
      lastName="???";
   }
}

Answer 1

Guest should assign whatever default you think best, perhaps null :

public Guest() {
    firstName = null;
    lastName = null;
}

And your code creating it:

seating[i][j] = new Guest();

But :

• Guest should probably provide a constructor that accepts the initial value to assign those as arguments

   public Guest(String _firstName, String _lastName) { firstName = _firstName; lastName = _lastName; } 

• Guest 's firstName and lastName probably shouldn't be public ; instead, make them private and use accessor functions. Opinions can vary on this, but it's the overwhelming convention in Java, and don't worry, the JVM is very good at making those accessors efficient.

• (Subjective) Opinions vary, but I find always explicitly using this when referencing instance members helps avoid confusion between variables, arguments, and instance members:

   public Guest(String firstName, String lastName) { this.firstName = firstName; this.lastName = lastName; } 

  Again, though, that's a matter of opinion and style.