When I print the constant in main, the static block does not execute, but when I print stat, it does execute. Is there any importance to static final in Java?
package com.test.doubt;
class Doubt {
public static final int constant = 123;
public static int stat = 123;
static {
System.out.println("Static Block");
}
}
public class MyProgram {
public static void main(String[] args) {
System.out.println(Doubt.constant);
}
}
Your code isn't initializing the Doubt class, precisely because Doubt.constant is a constant. Its value is baked into MyProgram at compile-time - you could even delete Doubt.class after compilation and your program would still run.
Run
javap -c com.test.doubt.MyProgram
to have a look at exactly what your code looks like after compilation.
See section 15.28 of the JLS for what constitutes a constant expression. For example, this would still be a constant:
public static final String FOO = "Foo";
and so would all of these:
public static final String FOO = "Foo";
public static final String BAR = "Bar";
public static final String FOOBAR = FOO + BAR;
... but this wouldn't be
public static final String NOT_A_CONSTANT = "Foo".substring(0, 1);
javac compiler optimised away the need for the Doubt class.
package com.test.doubt; class Doubt{ public static final int constant = 123; public static int stat = 123; static { System.out.println("Static Block"); } } public class MyProgram { public static void main(String[] args) { // System.out.println(Doubt.constant); System.out.println(Doubt.stat); } } but this code prints the static block,hence i get confused
The static final int will get compiled directly into your code as its value. That is to say, the JVM sees and is executing:
System.out.println(123);
and you're not touching your aptly-named Doubt class at all (this is an argument for not specifying constants in this fashion, btw. If you change that value you have to recompile every referencing class)
