Referenec passing

[tony kanvas]

public class ton{
  static String str = "Outside varaible";
  static void modify(String a){
    str = "a";
  }
  public static void main(String args[]){
    String str = "Inside variable";
    ton i = new ton();
    modify(str);
    System.out.println(i.str);
  }
}
// could you please explain to me the different between this tow class with regards to member variable str
public class Ian2{
  static int str = 22;
  static void modify(int a){
    str = a;
    str++;
    str++;
  }
  public static void main(String args[]){
    int str = 21; // here the local variable is 21.
    Ian2 i = new Ian2();
    modify(str); 
    
    System.out.println(i.str);
  }
}

[ Jess added UBB [code] tags to preserve whitespace ]
[ February 01, 2003: Message edited by: Jessica Sant ]

[Marilyn de Queiroz]

class ton{
    
    static String str = "Outside variable";
    
    static void modify( String a ){
        str = "a" ;
    }
    
    public static void main( String args[] ){
        String str = "Inside variable";
        modify( str );
        System.out.println( ton.str );
    }
    
}
    
class Ian2{
    
    static int str = 22;
    
    static void modify( int a ){
        str = a ;
        str++ ;
        str++ ;
    }
    
    public static void main( String args[] ){
        int str = 21; // here the local variable is 21.
        modify( str ); 
        System.out.println( Ian2.str );
    }
    
}

// could you please explain to me the difference between these two classes with regards to member variable str

First of all, I think it is a bad idea to assign an int to a variable named str. I suggest that you rename it to "number".
Second, str is not a member variable at all. It is a class variable and a local variable, but never a member variable. Because they are class variables, you do not need to instantiate the class in order to print them.

Thirdly, I'm not quite sure I understand what your question about these two class variables is. One is a String and the other is an int. Can you be a little more specific?
[ February 02, 2003: Message edited by: Marilyn de Queiroz ]

[tony kanvas]

Marilyn de Queiroz
Second str is not a member variable at all. It is a class variable and a local variable, but never a member variable. Because they are class variables, you do not need to instantiate the class in order to print them.
First I was playing in code so I didn�t take care about constants
Second That what I want to know:
when we call the String or StringBuffer (Object)it will call class var
And if we call any number then we use local var is this true
Thanks for your time

[Marilyn de Queiroz]

First I was playing in code so I didn�t take care about constants

They are not constants, they are class variables.
when we call the String or StringBuffer (Object)it will call class var
And if we call any number then we use local var is this true

Ummm, not exactly.

1  class ton{
2      
3      static String str = "Outside variable";
4      
5      static void modify( String a ){
6          str = "a" ;
7      }
8      
9      public static void main( String args[] ){
10         String str = "Inside variable";
11         modify( str );
12         System.out.println( ton.str );
13     }
14    
15 } 

String constant "Outside variable" is assigned to String str class variable in line 3.

String constant "Inside variable" is assigned to String str local variable in line 10.

In line 11, you send the contents of local variable str (currently set to "Inside variable" ) to method modify().

Method modify assigns "a" to class variable str in line 6. So it no longer is "Outside variable".

Line 12, System.out.println( ton.str ); prints the class variable because you told it to. If you just print str rather than ton.str or i.str, you will get the contents of the local variable str.

1  class Ian2{
2    
3      static int str = 22;
4    
5      static void modify( int a ){
6          str = a ;
7          str++ ;
8          str++ ;
9      }
10    
11     public static void main( String args[] ){
12         int str = 21;
13         modify( str ); 
14         System.out.println( Ian2.str );
15    }
16    
17 }

int constant 22 is assigned to int str class variable in line 3.

int constant 21 is assigned to int str local variable in line 12.

In line 13, you send the contents of local variable str (currently set to 21 ) to method modify().

Method modify assigns the local int variable that you passed (21) to class variable str in line 6. Now local variable str and class variable str are the same int value.

Then you add 1 twice to the class variable str.

Now when you return to main and print, you again request the class variable str to be printed rather than requesting the local variable str to be printed. (See above)

[Marilyn de Queiroz]

Perhaps it would be clearer if you changed the variable names. What you have could be written this way:

class ton{
    
    static String classStr = "Outside variable";
    
    static void modify( String a ){
        classStr = "a" ;
    }
    
    public static void main( String args[] ){
        String localStr = "Inside variable";
        modify( localStr );
        System.out.println( classStr );
    }
    
}
    
class Ian2{
    
    static int classNumber = 22;
    
    static void modify( int localNumber ){
        classNumber = localNumber ;
        classNumber++ ;
        classNumber++ ;
    }
    
    public static void main( String args[] ){
        int localNumber = 21;
        modify( localNumber ); 
        System.out.println( classNumber );
    }
    
}

[tony kanvas]

Thank you very much for your help
best wishes
tony (sweden)

[Jose Botella]

IMHO the members of a class are the fields, methods and nested types both declared and inherited in that class.
Constructors, static initializers and instance initializers are not members and they are not inherited.