Una pregunta sencilla y rápida en JAVA

http://www.seas.gwu.edu/_{drum/java/faq/faq.html}

Does Java initialize uninitialized variables for you?

Yes and no. Yes, in the sense that all variables are given a default value, but no in the sense that the compiler will somtimes complain about uninitialized local variables.

The initial values are quite logical: zero for numbers, false for boolean's and null for object references.

Thus, for example (source file), the following compiles without complaint. The instance variables get their default values.

public class test_init_var {
  double x;
  int[] A;
  char c;
  test_init_var t;

  public static void main (String[] argv)
  {
    test_init_var tiv = new test_init_var ();
    System.out.println ("x = " + tiv.x);
    System.out.println ("A = " + tiv.A);
    System.out.println ("c ='" + tiv.c + "'");
    System.out.println ("t = " + tiv.t);
  }
}

This will print out:

x = 0.0
A = null
c =''
t = null

However, for local variables, the compiler will often try to track down instances of uninitialized variables and will force you to do something about it. For example, the following will not compile: (source file)

public class test_init_var {
  public static void main (String[] argv)
  {
    double x2;
    int[] A2;
    char c2;

System.out.println ("x2 = " + x2);
System.out.println ("A2 = " + A2);
System.out.println ("c2 ='" + c2 + "'"); 
  }
}