Java Tutorial – Language Syntax and Structure
Java Tutorial – Language Syntax and Structure
In this post we discuss the Java Language Syntax and Structure. We will offer a cursory view of the Java language syntax and general structure of Java source code. It is my hope that this will give you enough knowledge to get you started in the right path in Java. Subsequent posts will provide more detail on Java language syntax and structure.
What’s Covered
Language Syntax and Structure
Java Naming Conventions
Java follows Naming Conventions Standards in order to make the program more readable as hence easier to read and understand.
Packages
Java Packages are always written in lowercase domain name order. For example, if your company was avaldes.com then it would be written as com.avaldes.tutorial the general format is, tld.domain.project.subproject. The TLDs currently in use are .com, .net, .org, .mil, .gov, .edu or one of the two-letter ISO country codes like .us, .in, .ca, .jp, .cn.
Defining Packages
package com.avaldes.util;
or
Use Packages via import
import org.apache.http.client.HttpClient; import org.apache.log4j.Logger; import java.nio.channels.FileChannel;
Classes
Class names should be nouns, mixed case with the first letter of each internal word capitalized (CapitalCamelCase).
public class Person { ... } public class Customer { ... } public class RestfulSecurityExample { ... }
Interfaces
Interfaces should be capitalized like classes, mixed case with the first letter of each internal word capitalized.
public interface Circle { ... } public interface Serializable { ... } public interface Animal { ... }
Methods
Methods should be verbs, in mixed case with the first letter lowercase, with the first letter of each internal word capitalized.
private void eat() public boolean getData() public void run()
Variables
Variable names should be kept as short as possible yet maintain meaning. Variables should be in mixed case with the first letter lowercase and the first letter of each internal word capitalized.
boolean isActive = false; int quantityOnHand = 0; int i;
Constants
Constant names, by convention, are in all upper case with multiple words delimited by underscope ‘_’ character.
private static final int MAX_FILES = 25; private static final String FILENAME = "output.txt";
Java Separators
The Java language makes use of certain special characters as separators. Each of these special characters play an important role in Java.
Curly Braces {}
- Used to mark the start and end of a code block
public class MyClass { ... }
int dataPoints[] = {10, 7, 8, 12, 17, 28, 39, 65, 28};
or
int[] dataPoints = {10, 7, 8, 12, 17, 28, 39, 65, 28};
Parentheses ()
- Used in method declaration for list of parameters
public void calcSales(float price, int quantity) { ... }
System.out.println();
long lg = 786; int i = (int) lg;
while (i < 10) { ... i++; }
or
for (int i=0; i<10; i++) { ... }
Brackets []
- Used in array declaration
public int months[] = new int[12];
for (int i = 0; i < months.length; i++) { System.out.format("Month %d = %d\n", i, months[i]); }
Angle Brackets <>
- Used to specify Generics in Java
List<Employee> employees = new ArrayList<Employee>(); Map<String, Player> players = new HashMap<String, Player>();
Semicolon ;
- Used for terminating statements in Java and as separators in the for loop
int cars = 0; boolean isActive = false; for (int i = 0; i < 10; i++) { ... }
Colon :
- Used in the for loop for collection and array
for (String playerID : playerMap.keySet()) { ... }
Comma ,
- Used to separate elements in array initializer and parameter separator in methods
int[] dataPoints = {10, 7, 8, 12, 17}; public void displayAt(int x, int y, String message) { ... }
Period .
- Used in package names (reverse order) as a separator between the TLD (Top-Level Domain) and domain name, sub-domain, etc and used in classes to separate methods or fields
package com.avaldes.tutorial; logger.info("Status: " + status);
Java Integer Literals
Java Integer Literals are a sequence of digits that represent constant values that are stored in variables.
int intValue = 100; int octalValue = 0529; int hexValue = 0xBA9E;
Java Integer Literals in Java 7
Starting in Java 7, the underscore character ‘_’ may be used anywhere between digits in a numeric literal. By doing this the developers of Java have improved the readability of your code.
int intValue = 100000000; int intValue1 = 100_000_000; // more readable int hexValue = 0xBABE_CAFE; int byteValue = 0b0110_0011_1101_1100; int notAllowed = 100_000_000_; // cannot put at the end
Java Long Literals
To distinguish a long from an integer we use the letter L or l. However, L is the preferrable choice since it is more readable than the lowercase l which can easily be confused with the digit 1.
long l1 = 1300L; long l2 = 76403872093L;
Java Long Literals in Java 7
long l3 = 76_403_872_093L; long socialSecurity = 182_18_6833L; long creditCard = 3872_6672_2939_8200L;
Java Floating Literals
Floating-point literals of type float end with the letter F or f. If we are using type of double it should end with the letter D or d.
float f1 = 254.9f; float f2 = 18249.75F; double d1 = 27500.29d; double d2 = 36050.99D; double d3 = 17_500_800.99D;
Java Character Literals
Literals of type char contain any Unicode (UTF-16) character or an escape sequence enclosed in single quotes.
char c1 = 'a'; char c2 = 'M'; char c3 = '%'; char s1 ='\b'; // backspace char s2 ='\t'; // tab char s3 ='\\'; // backslash char s4 ='\"'; // double quotes char s5 ='\''; // single quote char s6 ='\n'; // linefeed char s7 ='\r'; // carriage return
Java Class Literals
Java supports the concept of class literals by appending the keyword .class; for example String.class, double.class, long.class, or our own classes for example, Person.class or Customer.class.
Class PersonObject = Person.class; Person person = (Person) PersonObject.newInstance();

Core Java Related Tutorials
- Base64 Encoding and Decoding Examples in Java 8
In this tutorial we will discuss how to Encode and Decode using Base64 using Java 8, which now finally has native Base64 support. - Base64 Encoding and Decoding Examples in Java using Google Guava
This tutorial will introduce how to Encode and Decode using Base64 using Google’s Guava Project Open Source library. - Base64 Encoding and Decoding Examples in Java using Apache Commons
This tutorial will introduce Base64 encoding and decoding examples using the Apache Commons Codec library. - Custom Number Formatting in Java
In this example we will show you how to use the NumberFormat and DecimalFormat classes to format numbers using special patterns. - Custom Date Formatting in Java
In this example we will show you how to use the SimpleDateFormat class to format Date objects using special patterns to better fit the needs of the application.
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