Michael Ardan Michael Ardan - 4 years ago 215
Java Question

Java - Default Values and Initialization

Based on my reference, primitive types have default values and Objects are null. I tested a piece of code using both NetBeans and Eclipse.

public class Main {
public static void main(String[] args) {
int a;
System.out.println(a);
}
}


Using both IDE, the line
System.out.println(a);
will be an error pointing at the variable
a
that says
variable a might not have been initialized
whereas in the given reference,
integer
will have
0
as a default value. However, with the given code below, it will actually print
0
.

public class Main {
static int a;
public static void main(String[] args) {
System.out.println(a);
}
}


What could possibly go wrong with the first code? Does instance variable behaves different from local variables?

Answer Source

In the first code sample, a is a main method local variable. Method local variables need to be initialized before using them.

In the second code sample, a is class member variable, hence it will be initialized to default value .

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