Initializing Variables - top of Musings page

By: Nicholas Duchon.

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There are three ways to declare new variables in java:

1. as class variables, either instance or static;
   
2. as method variables
   
3. as method parameters (input to a method)

Basic layout:

class A {
  // initializing a class instance variable:
  String s = "this is it";

  // initializing a class static variable:
  static int counter = 0; 

  // parameters to a method:
  // the varables abc, def and spr are initialized as
  // part of the calling operation by the caller
  int mA (int abc, double def, String spr) {

    // the following variables are method variables
    // these variables are only visible in this method
    // if you define any of these variables 
    // in another method in this
    // class, they will not be the same variables as far as 
    // java is concerned - same name but different items.
    // This is something like two people being called 
    // John Smith - names the same but not the same people
    double dd = 17.5;
    float ff = 17.5f;
    float fg = (float) 17.5;

    // note: without the f on 17.5 on the ff initialization
    // or the (float) cast on the fg init, the java compiler
    // will give a "narrowing" casting error - indicating a
    // a potential, unintentional, loss of precision.

    // this is because java assumes that literals, like
    // 17.5, are by default of type double.

  } // end method mA
} // end class A

An additional note:

In the following code segment, ig is not initialized for certain, and the compiler will flag an error:

  int ix = 2;
  int ig;
  if (ix < 3) 
    ig = 5;
  ig = ig + 3;

The error will not be flagged until ig is actually used (as an r-value for those who are more advanced), which in this case, occurs on the last line.

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ND.