JAVA EE: Java Tutorial : Java nested classes(Local Classes-Static)

Monday, 11 January 2016

Java Tutorial : Java nested classes(Local Classes-Static)

Click here to watch in Youtube :
https://www.youtube.com/watch?v=CkB1c2ntc_4&list=UUhwKlOVR041tngjerWxVccw

OuterClass.java

public class OuterClass
{

    private String name = "John";

    public void greetInEnglish()
    {
        class SayHello
        {
            /*
             * We cannot declare static variable or static methods in a local
             * class.
             */

            public static String message = "Welcome";

            public static void greet()
            {
                System.out.println(message);
            }
        }

        SayHello sayHello = new SayHello();
        sayHello.greet();

    }
}

LocalClassTest.java

public class LocalClassTest
{
    public static void main(String args[])
    {
        OuterClass outerClass = new OuterClass();
        outerClass.greetInEnglish();
    }

}

Output

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    The field message cannot be declared static in a non-static inner type,     
    unless initialized with a constant expression
    
    The method greet cannot be declared static; static methods
    can only be declared in a static or top level type

    at OuterClass$1SayHello.<init>(OuterClass.java:15)
    at OuterClass.greetInEnglish(OuterClass.java:23)
    at LocalClassTest.main(LocalClassTest.java:7)