Presentation is loading. Please wait.

Presentation is loading. Please wait.

1 Introduction to Java Brief history of Java Sample Java Program Compiling & Executing Reading: => Section 1.1.

Similar presentations


Presentation on theme: "1 Introduction to Java Brief history of Java Sample Java Program Compiling & Executing Reading: => Section 1.1."— Presentation transcript:

1 1 Introduction to Java Brief history of Java Sample Java Program Compiling & Executing Reading: => Section 1.1

2 2 Introduction to Java Introduction to Java History Invented in 1991 - Sun Microsystems, Inc (James Gosling). Sun Microsystems was purchased by Oracle Corporation in 2010. Originally a language for programming home appliances. Later (1994) used for internet applications and general-purpose programming. Why the name “Java”?  Supposedly came from a list of random words (wikipedia).

3 3 A Java Application import java.util.Scanner; public class FirstProgram { public static void main(String[] args) { int n1, n2; Scanner keyboard = new Scanner(System.in); System.out.println(“Enter an integer:”); n1 = keyboard.nextInt(); System.out.println(“Enter another integer:”); n2 = keyboard.nextInt(); System.out.println(“The sum is:”); System.out.println(n1 + n2); } >javac FirstProgram.java >java FirstProgram Enter an integer: 15 Enter another integer: 7 The sum is: 22 >

4 4 Explanation of Code... Code at the beginning of the program (to be explained later): import java.util.Scanner; public class FirstProgram { public static void main(String[] args) { Java applications all have similar code at the beginning  The name of the class differs from one program to another.  The name of the class is also the name of the file.  Notice that the blank line is gone!

5 5 … Explanation of Code... The following creates two variables named n1, n2 for storing two whole numbers (integer): int n1, n2; These are called “variable declarations.” In this program they are used to store the user’s response.

6 6 … Explanation of Code... The following creates an object called keyboard of the Scanner class: Scanner keyboard = new Scanner(System.in); System.in refers to the keyboard The Scanner class provides the program with access to keyboard input.

7 7 Explanation of Code... Displays a “text” string to the screen: System.out.println(“Enter an integer:”); Note the “dot” delimiter:  System is a class  out an object  println is a method that outputs something Double-quoted text inside the parentheses is referred to as an argument or parameter to the method.

8 8 … Explanation of Code... The following inputs (or “reads”) an integer typed in using the keyboard and stores it in the variable n1 : n1 = keyboard.nextInt(); The next two lines are similar: System.out.println(“Enter another integer:”); n2 = keyboard.nextInt();

9 9 … Explanation of Code The following prints the sum to the console (or screen): System.out.println(“The sum is:”); System.out.println(n1 + n2); By the way, every character counts!

10 10 Compiling and Running a Java Program Type the program into a file:  FirstProgram.java Make sure you get the file name correct! Compile (from the command-line, i.e., DOS):  javac.java Run (and link):  java

11 11 Extra Work – Yippee! Type-in, compile and run the previous program. Experiment with “what if” scenarios:  Add some syntax errors  Run the program incorrectly – input improper data  Modify the program to work with 3 ints Note that if you change the program, you have to recompile before you rerun!

12 12 Some Helpful Commands Some helpful commands:  cd - change directory  cd..- move up a directory  dir - list directory contents matching the pattern  mkdir - create a new directory  del - delete a file or files matching the pattern Suggestion – create a new directory/subfolder on your “C” drive to store all class related programs. Create subfolders as appropriate.


Download ppt "1 Introduction to Java Brief history of Java Sample Java Program Compiling & Executing Reading: => Section 1.1."

Similar presentations


Ads by Google