Chapter 1 – Introduction

Identifiers

Names for classes, methods, variables, etc are called Identifiers

Rules for valid identifiers:

Made up of letters, digits, the underscore character ("_") and the dollar sign

Cannot begin with a digit

Keywords are excluded (eg public, static, void, new, true, false, null)

Keywords

Java Keywords have a special meaning

From the Java Language Specification:

The following character sequences, formed from ASCII letters, are reserved for use as keywords and cannot be used as identifiers:

Keyword: one of
    abstract      for              switch
    assert        if               synchronized
    boolean       goto             this
    break         implements       throw
    byte          import           throws
    case          instanceof       transient
    catch         int              try
    char          interface        void 
    class         long             volatile
    const         native           while                        
    continue      new       
    default       package   
    do            private   
    double        protected 
    else          public    
    enum          return    
    extends       short     
    final         static    
    finally       strictfp  
    float         super

Choose Meaningful Names

You should choose names that are

Variables names should indicate what the variable holds

For example: String river = "Mississippi";

Capitalization

Someone asked how to know what to capitalize:

Answer: follow conventions

Classes: Capitalize and Camel
Variables and Methods: lower case and Camel

Camel: capitalize words following first

We will learn other conventions later

More on Comments

There are three kinds of comments

// Everything to the end of the line is ignored
/* ... */ Everything within this pair is ignored

Can span multiple lines
Can NOT be nested

/** ... */ Used to generate html documentation

Programs Need to be General

A program should be general, not specific

It should solve any version of a given problem

Example: Swap 'e' and 'o' in any string, not just in "Hello"