![Variable Initialization
//********************************************************************
// PianoKeys.java Author: Lewis/Loftus
//
// Demonstrates the declaration, initialization, and use of an
// integer variable.
//********************************************************************
public class PianoKeys
{
//-----------------------------------------------------------------
// Prints the number of keys on a piano.
//-----------------------------------------------------------------
public static void main (String[] args)
{
int keys = 88;
System.out.println ("A piano has " + keys + " keys.");
}
}](https://image.slidesharecdn.com/hf9hy1yrqdgik5ibfszc-140524210929-phpapp02/85/Chapter-3-1-9-320.jpg)
![Variable Initialization
//********************************************************************
// PianoKeys.java Author: Lewis/Loftus
//
// Demonstrates the declaration, initialization, and use of an
// integer variable.
//********************************************************************
public class PianoKeys
{
//-----------------------------------------------------------------
// Prints the number of keys on a piano.
//-----------------------------------------------------------------
public static void main (String[] args)
{
int keys = 88;
System.out.println ("A piano has " + keys + " keys.");
}
}
Output
A piano has 88 keys.](https://image.slidesharecdn.com/hf9hy1yrqdgik5ibfszc-140524210929-phpapp02/85/Chapter-3-1-10-320.jpg)
Chapter 3.1
- 1. DECLARING AND USING IDENTIFIERS, VARIABLES AND CONSTANT Chapter 3.1:
- 2. Name of things such as variables, constants, name of classes and methods, that appears in programs. Example: Variable: num1 Constant: PIE Method: countNum() Identifiers
- 3. Java’s Rules for Identifiers Can be made of ONLY letters, digits, (_) and $. Cannot start with a digit. Spaces are not permitted inside identifiers. Cannot use reserved words. e.g: int,public, throws,return An identifier cannot be true, false, or null. They are case sensitive. An identifier can be of any length.
- 4. Variables A variable is a name for a location in memory that holds a value. Is used to store data input, data output, or intermediate data Representing data of a certain type Content may change during program execution. Must be declared before it can be used. May not be automatically initialized. If new value is assigned, old one is destroyed. Value can only be changed by an assignment statement or an input (read) statement.
- 5. Java Keywords abstract assert boolean break byte case catch char class continue default do super switch synchronized this throws transient try void volatile while • double • else • enum • extends • for • final • finally • float • if • implements • import • instanceof • int • interface • long • native • new • package • private • protected • public • return • short • static • strictfp*
- 6. Declaring Variables Syntax: datatype variableName Example: int i,j; //Declare i and j to //be an integer variable; double sale; //Declare sale to // be a double variable; char first; // Declare first to be a // character variable; String str; // Declare str to be a //String variable;
- 7. Declaring Variables A variable declaration specifies the variable's name and the type of information that it will hold int total; int count, temp, result; Multiple variables can be created in one declaration data type variable name
- 8. Variable Initialization A variable can be given an initial value in the declaration int sum = 0; int base = 32, max = 149; When a variable is referenced in a program, its current value is used See PianoKeys.java
- 9. Variable Initialization //******************************************************************** // PianoKeys.java Author: Lewis/Loftus // // Demonstrates the declaration, initialization, and use of an // integer variable. //******************************************************************** public class PianoKeys { //----------------------------------------------------------------- // Prints the number of keys on a piano. //----------------------------------------------------------------- public static void main (String[] args) { int keys = 88; System.out.println ("A piano has " + keys + " keys."); } }
- 10. Variable Initialization //******************************************************************** // PianoKeys.java Author: Lewis/Loftus // // Demonstrates the declaration, initialization, and use of an // integer variable. //******************************************************************** public class PianoKeys { //----------------------------------------------------------------- // Prints the number of keys on a piano. //----------------------------------------------------------------- public static void main (String[] args) { int keys = 88; System.out.println ("A piano has " + keys + " keys."); } } Output A piano has 88 keys.