Java Stylistic Conventions Object-Oriented Programming with Java: An Introduction by David J. Barnes Published by Prentice-Hall

Introduction

Comments

• purpose
• argument descriptions
• result descriptions
• constraints
• exceptions thrown

        /** Locate the minimum value in the elements
         *  data[lower .. upper].
         *  Lower must be <= upper, and both must be within the
         *  range 0 .. data.length-1.
         *  @param data The data to be searched.
         *  @param lower The lowest index for the range to be searched.
         *  @param upper The highest index for the range to be searched.
         *  @return The minimum value.
         *  @throws IllegalRangeException if lower > upper, or either
         *          lower or upper is outside the bounds of data.
         */
    public int locateMin(int[] data,int lower,int upper)
                        throws IllegalRangeException {
        ...
    }

    /* This comment
       is a multi-line comment
       that spans several lines.
     */

    /* This comment
     * is a multi-line comment
     * that spans several lines.
     */

Identifiers

if(list.point() == -1)

if(list.getNumberOfItems() == 0)

• Loop-control variables in for-loops used to systematically iterate over a fixed range.
• The formal argument name of a simple set mutator method. The name will typically be the first letter of the attribute being mutated.

Final Variables

final int endOfList = -1;
final int meaning = 42;
final double MAXMARK = 100.0;

class Date {
    public static final int January = 0, ... ;
    ...
}

Indentation and Layout

class ExampleClass {
    public static final int LOW = -20, MEDIUM = 0, HIGH = 20;
    public static final int DEFAULT = MEDIUM;

    public ExampleClass(int initialValue){
        if(howMany > DEFAULT){
            setNumber(initialValue);
        }
        else{
            setNumber(DEFAULT);
        }
    }

    ...

    private void setNumber(int number){
        this.number = number;
    }

    private int number;
}

VeryLongClassName evenLongerVariableName =
                        new VeryLongClassName("Say hello to auntie.");
Greeting introduction = new Greeting("Good morning,",32,'x',
                                     new Point(8,105),
                                     new Point(458,47));

Initializers and Anonymous Classes

int[] values = {
    3, 56, 23, 999, 101, -8, 3443, 23234, -9900,
    45, -349730, 783,
};

button.addActionListener(new ActionListener(){
    public void actionPerformed(ActionEvent e){
        ...
    }
});

Curly Brackets

class ExampleClass {
    public void method(){
        ...
    }
}

if(x > largest){
    largest = x;
}

if((month < rainfall.length) &&
        (rainfall[month] > greatest)){
    statement;
}

Increment and Decrement Operators

    arr[index++] = reader.nextInt();

    arr[index] = reader.nextInt();
    index++;

Switch Statement

Exceptions

• Use checked exceptions whenever possible.
• Include a throws-clause for unchecked exceptions even though this is not mandatory.
• Take the opportunity to create sub classes of the basic Exception classes in order to give meaningful names to the types of errors that arise. These do not need to add additional attributes or behavior to their super class. Where such new exception classes are closing tied to a single throwing class, consider defining them as static nested classes within the throwing class.
• Use exceptions for `impossible routes' through methods. These will often be thrown in a final else-part of a validity-checking cascading if-else statement, or at the end of a result-returning method that should be unreachable in normal circumstances.

Access Control

• An object's attributes should always be declared as private, rather than public, package or protected, even if the class is to be extended.
• Access to private attributes of primitive type may safely be granted via accessors with public access. Greater care should be taken when returning references to private attributes of object types since this could potentially allow circumvention of validating mutators via an alias. Use either public or protected access as appropriate.
• Use protected access mutators as a general rule, unless public access is required. Public access mutators should take particular care over validation of their arguments to ensure that an object is not left in an inconsistent state.
• Methods intended purely for internal use by a class should be protected, to make possible future extension by classes in other packages easier than with package access.
• General methods intended for the receipt of messages from other classes should be public.
• Constructors should normally provide either package or public access. If the class has package access, then no harm is done in providing public constructors.
• Classes and interfaces should have either package or public access, depending upon a program's requirement.

The Main Method

Threads