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Java Intro

Java Intro. A First Java Program. //The Hello, World! program in Java public class Hello { public static void main(String[] args) { System.out.println("Hello, World!"); } }. A First Java Program. //The Hello, World! program in Java Comments start with //

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Java Intro

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  1. Java Intro

  2. A First Java Program //The Hello, World! program in Java public class Hello { public static void main(String[] args) { System.out.println("Hello, World!"); } }

  3. A First Java Program • //The Hello, World! program in Java • Comments start with // • Comment goes to the end of the line • Multiline comments start with /* and end with */ • /*This is a multiline • comment */

  4. A First Java Program • public class Hello { • } • Definition for the class Hello • Class Hello MUST be defined in a file named Hello.java • The class definition is enclosed in {}

  5. A First Java Program • public static void main(String[] args) { • } • Every Java application must have a main method • The header of every main method looks the same • The method is enclosed by {} • Whitespace is ignored • Proper indentation is not required by the compiler • But, it is required by the instructor...

  6. A First Java Program • System.out.println("Hello, World!"); • Print the string enclosed by the quotation marks • Every statement must end with a semi-colon • Double quotes enclose strings

  7. Java Compiler High-level Code Bytecode Interpreter (JVM) Output

  8. Writing/Compiling/Running • Write the program using your favorite text editor – save a class classname into file classname.java • Open a terminal window and cd into the directory where your code is saved • To compile, type javac classname.java • Fix any errors and go back to step 3 • To run, type java classname

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