Java Language Summary.pdf

A P P E N D I X A

Java LanguageSummary

A P P E N D I X A


A P P E N D I X A


This appendix contains a summary of the Java language that you can use as a quick reference.

Reserved WordsThe following is a list of Javas reserved words, also known as keywords.You cannot use them to name identifiers.

The boolean literals true and false, and the null literal, while not technicallykeywords, cannot be used as identifiers.

3

abstract default if private this

boolean do implements protected throw

break double import public throws

byte else instanceof return transient

case extends int short try

catch final interface static void

char finally long strictfp volatile

class float native super while

const for new switch

continue goto package synchronized

Primitive Data TypesThere are eight primitive data types in Java. They are listed here, alongwith the number of bits used for each type. The ranges of possible valuesfor the integral types are provided. Floating point constants that representundefined numbers are also provided here for your reference.

4 Learn java In a Weekend

TABLE A.1 PRIMITIVE DATA TYPE LISTING

Type Number of Bits

boolean 1

byte 8

short 16

char 16

int 32

float 32

long 64

double 64

*NaN stands for not a number and represents values of undefined operations suchas 0.0 / 0.0.

APPENDIX A Java Language Summary 5

TABLE A.2 RANGES FOR INTEGRAL TYPES

Type Minimum Maximum

byte -27 27 1

short -215 215 1

int -231 231 1

long -263 263 1

char 0 216 1

TABLE A.3 FLOATING POINT CONSTANTS

Float.NEGATIVE_INFINITY

Float.POSITIVE_INFINITY

Float.NaN*

Doube.NEGATIVE_INFINITY

Double.POSITIVE_INFINITY

Double.NaN*

CommentsThree types of comments are used in Java (single line, multi-line, andjavadoc).

Single line comment example:

// this is a single line comment

Multi-line comment example:

/* this is a multi-line

comment */

Javadoc comment example:

/**

* This Is a javadoc comment

*/

LiteralsLiterals are used in Java to represent values that are of the primitive,String, or null types in source code. To summarize their syntaxes, any-thing within square brackets ([ and ]) is optional, whereas the bar char-acter (|) separates different options; for example, [+|-] means either +,-, or neither (since they are within square brackets).

Integer LiteralsInteger literals can be expressed in octal (base 8), decimal (base 10), orhexadecimal (base 16). Octal digits can be any digit from 0 to 7. Decimaldigits can be any digit ranging from 0 to 9. Hexadecimal digits can be anydigit ranging from 0 to 9 and also any letter (case insensitive) from A to F.A=10, B=11, C=12, D=13, E=14, F=15. The syntax for an integer literal is

[+|-][0[X|x]]number[L|l]


Floating Point LiteralsA floating point literal can be either a float or a double. The syntax fora floating point number is

[+|-]number.number[[+|-]Eexponent|[+|-]eexponent][F|D|f|d]


Example Description

67 int literal having value 67

+67 int literal having value 67

-67 negative int literal having value 67

012 octal int literal having value 10

-0X27C hexadecimal int literal having value 636

1234567890L long literal having value 1,234,567,890

-0XBEL hexadecimal long literal having value -190

Example Description

-10. double literal having value -10.0

+.01 double literal having value 0.01

1.23 double literal having value 1.23

1.23d double literal having value 1.23

1.23f float literal having value 1.23

2E4 double literal having value 20,000.0 (2x104)

-133e-2F float literal having value -1.33 (-133x10-2)

Boolean LiteralsBoolean literals must be either true or false.

Character LiteralsA character literal is a single character, or escape sequence enclosed in singlequotes. The data type of a character literal is always char. A Unicode char-acter escape sequence is in the form \unnnn, where nnnn is the hexadecimalrepresentation of the character. The syntax for a character literal is

character|escape_sequence

Exactly one character or escape sequence must appear within the singlequotes.


Example Description

a char literal a

$ char literal $

\u003F char literal ?

\ char literal (single quote)

\ char literal (double quote)

\b char literal for backspace

\f char literal for formfeed

\n char literal for new line

\r char literal for carriage return

\t char literal for tab

\\ char literal for backslash (\)

String LiteralsA string literal consists of a string of characters and/or escape sequenceswithin double quotes. The data type is always String. The syntax for aString literal is

[characters&|escape_sequences]

Null LiteralThe null literal is null.

OperatorsBelow, arg refers to any variable or value. Some operators take onlycertain types of arguments. For example, ! works only on boolean types.


Example Description

An empty string

Abc String literal Abc

\Java\ String literal Java

C:\\My Documents\\myfile.txt String literal C:\MyDocuments\myfile.txt


Type Syntax Description

Unary +arg, -arg Sign (positive or negative)

++variable Prefix increment

variable++ Postfix increment

--variable Prefix decrement

variable-- Postfix decrement

!arg Boolean compliment (Not)

~arg Bitwise inversion

(type)arg Cast

Arithmetic arg + arg Addition

arg - arg Subtraction

arg * arg Multiplication

arg / arg Division

arg % arg Modulus

Shift arg >> arg Left shift

arg >> arg Right shift

arg >>> arg Unsigned right shift


Type Syntax Description

Comparison arg < arg Less than

arg > arg Greater than

arg = arg Greater than or equal to

arg == arg Equal to

arg != arg Not equal to

arg instanceof class Instance of

Bitwise arg & arg Bitwise AND

arg | arg Bitwise OR

arg ^ arg Bitwise XOR

Logical arg && arg Logical AND

arg || arg Logical OR

Ternary condition ? val_if_true : val_if_false Conditional operator

Assignment OperatorsAssignment operators store a value in a variable. This section covers theoperators that include the equal sign (=). (The increment (++) and decre-ment (--) operators perform assignments as well, but are not covered inthis section.) The assignment operator can be just the equal sign or theequal sign followed by an additional operator (note that the combinationof the two constitutes one single operator). The syntax for the assignmentoperator is

variable =[op] arg

If = is combined with another operator, the operation is logically equiva-lent to

variable = variable op arg

The following are all assignment operators:

= += -= *= /= &= |= ^= %=

= >>>=

LoopsThis section summarizes the syntax used for the three types of loops: for,while, and do-while.


Name Syntax

for loop for([init, init, ];[condition];[update,update, ]) { body }

while loop while(condition) { body }

do loop do { body } while (condition);

Break and ContinueThe break and continue statements redirect the flow of loops. breakwill take control out of the loop and continue will return control backto the top of the loop.

ConditionalsThe conditional statements are if, and switch, as well as the Ternaryoperator described in the section Operators. The syntax for the if con-ditional is

if (condition) {

statements_condition_true;

}

[else if (other_condition) {

statements_other_condition_true;

}, ]

[else {

statements_no_condition_true;

}]

The square brackets in the previous code indicate that the else if andelse statements are optional and are not part of the syntax.

The syntax for the switch conditional is

switch (test) {

case value: [statements_test_equals_value] [break;]

[default: [statements_test_equals_no_case_value]

}


Try-Catch Blockstry-catch blocks are used for exception handling. Here is the syntax:

try {

statements_that_may_cause_an_exception;

} catch (exception_type exception_variable_name) {

[statements_that_execute_if_exception_is_caught]

} finally {

[statements_that_execute_whether_or_not_an_exception_occurs]

}

Class DefinitionThe syntax for defining a class is

[package package_name;]

[[import Imported_class_or_package;] ]

[access_modifier] class class_name [extends super_class_name][implements implemented_Interface, ] {

[class_definition]

}

Class ModifiersThis section describes the Java keywords used to modify classes.


Modifier Description

public Access modifier.

final Cannot be subclassed.

abstract Must be subclassed (cannot be instantiated).

Constructor DefinitionThe first line of the constructor body must be either an explicit call to thesuper-classs constructor using super(), an implied call to the super-classs no-arg constructor, or a call to another constructor within this classusing this(). The syntax for a constructor is as follows:

[access_modifier] class_name([arg, ]) { [constructor_body] }

Variable DeclarationThe syntax for declaring a variable is as follows:

[access_modifier] [modifier, ...] type variable_name [ = initial_value];

Variable ModifiersVariable modifiers are Java keywords that modify the characteristics of avariable.


Modifier(s) Description

public, protected, private Access modifiers.

static Used to indicate this is a class variable.

final Used to indicate a constant.

transient Used to indicate a variable thatcannot be serialized.

volatile Used to indicate that variable maybe modified asynchronously.

Method DefinitionUnless the return type is void, the last executable statement of any logicalpath of execution within the method must be a return statement thatreturns a value of type return_type. The syntax for defining a methodis as follows:

[access_modifier] [modifier, ] return_type method_name([arg, ])[throws exception, ] { [body] }

Method ModifiersMethod modifiers are Java keywords that are used to modify the charac-teristics of a method.


Modifier(s) Definition

public, protected, private Access Modifiers.

static Indicates this is a class method.

final Indicates that this method cannotbe overridden.

abstract Indicates the body must be definedin a subclass.

native Indicates the method body isdefined outside of Java in a nativelibrary.

synchronized Indicates that at most only onethread may have control of thismethod at any given time.

Java Language Summary.pdf

Documents

Transcript of Java Language Summary.pdf