Programming in Java I

Recap of Class 1

• Java programs are built from classes.
• All Java classes should begin with an uppercase character.
• If a class name consists of more than one word, each word should begin with an uppercase character.
• The Keyword class is used to define a class.
• The filename must be identical to the Java class that has the main method.
• The main method marks the beginning of a Java application.

public static void main(String [] args) {
     :
     :
}

• A block consists of 0, 1 or more statements enclosed in curly braces { } .
• A variable - is a named memory location.
• Variables are used to manipulate your programs data.
• Each variable must be associated with a type

int year;
double tax;
String name;

• The symbol = is called the assignment operator.
• We use the assignment operator to give a variable a value.

year = 2006;

• A variable can be declared and assigned in one step.

int year    = 2006;
String name = "Fred";

• The following window is referred to as a terminal window or the console.



• Method println is used to send data to the console.
• To send the String "Fred" to the console, we would write the command.

System.out.println("Fred");

• Can also output the value of a variable

int year = 2006;
System.out.println(year);   // sends 2006 to the console.

• A sequence of characters enclosed in quotes " " is a String literal or simply a String

"This is a String , remember strings are objects in Java";

• We can assign a String to a variable.

String name = "Assigning a string to a reference variable name";

• When one of the operands to the plus operator '+' is a string, string concatenation is performed.

String first = "Fred";
String name  = first + " Flintstone";
System.out.println(name);     // Fred Flintstone is sent to the console.

int year = 2006;
System.out.println("The year is " + year); // The year is 2006  is sent to the console.

• Commands or statements typically end with a semicolon ;

  Send Questions or Comments to javadepaul@yahoo.com
  © Anthony Larrain 2004 - 6