2. Hello World

The 'Hello World' program, of Tutorial 1, is described.

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The package refers to this folder structure.

// *** 1. Start ***
package com.javaAndroid.ex1;
// *** 1. End ***

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Class can be public or default (package-level). Public would be important for external libraries, such as standard Java classes such as java.lang.Math, which have to be used in almost any real application.

// *** 2. Start
public class Ex1 {
// *** 2. End

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The main() function is the entry-point of a java program.

 // *** 3. Start
 public static void main (String[] args) {
 // *** 3. End

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String is a utility class based on the char primitive.

  // *** 4. Start
  String hello = "Hello World!";
  // *** 4. End

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println() method is part of java.lang.System class.

  // *** 5. Start
  System.out.println(hello);
 }
}
// *** 5. End

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// *** 1. Start ***
package com.javaAndroid.ex1;
// *** 1. End ***

// *** 2. Start
public class Ex1 {
// *** 2. End

 // *** 3. Start
 public static void main (String[] args) {
 // *** 3. End

  // *** 4. Start
  String hello = "Hello World!";
  // *** 4. End
  
  // *** 5. Start
  System.out.println(hello);
 }
}
// *** 5. End

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