Simple java code showing that before we can assign value to variable it has to be known to the javac compiler in advance

JavaExample.java

public class JavaExample {
    // with the next line commented the code is erroring out when we try to compile it
    //public int number;

    public JavaExample (int _number) {
        number=_number;
    }

    public void show() {
       System.out.println("[test " + number + "] list=%s");
    }

    public static void main(String[] args) {
	JavaExample t=new JavaExample(1);
        t.show();
    }
}