Programming in Java language

The most important commands from Java programming language in one place, a unique comparison and each command-operator is shown using a piece of program. Statements-operators of these sample programs are clickable, so with a simple click we have more information available.

Programming language Java:

Lexical elements

Types and variables

Program structure

Operators

Statements

Lexical elements

Lexical elements are numeric, string constants and comments in the code.

Types and variables

Types and variables are closely related because variables are the most important elements of our program in which we store data, partial results of our calculations. Types tell us what data can be stored in variables.

Basic data types - Simple data types that can be numbers, characters, or logical types. They are suitable for storing one value.
- Logical Boolean data type: boolean
- Numbers - Types for storing numbers.
  - Integers - Types for storing integers.
    - Signed - Types for storing signed integers.
      8-bit integer: byte 16-bit integer: short 32-bit integer: int 64-bit integer: long
  - Real numbers 32-bit real number: float 64-bit real number: double
Type conversions - Using a type conversion we can change the type of existing types. Thanks to this we can overwrite automatic conversion.
- Explicit - By using an explicit conversion, you can specify exactly what type you want to work with. Thanks to this we can overwrite automatic conversion.
  To 8-bit integer To 16-bit integer To 32-bit integer To 64-bit integer To 32-bit real number To 64-bit real number To boolean
Variables - Variable is used for storing the data. can be declared in different locations and can be used in different locations. it can be distinguished according to the lifetime: they are global or local static variables. it is possible use in the structure or function.
Variable declaration Variable use
- Automatic variable - Automatic variable declaration is allowed almost anywhere, lifetime is usually from the declaration to the end of the current block.
  Automatic variable declaration

Program structure

Operators

Operators perform an operation between the operands, this operation can be mathematical, logical, or bitwise.

Parenthesis operator: ( )

Arithmetic operators - Are used to perform mathematical operations. the following are basic operations between the arithmetic operators:
Addition: + Subtraction: - Multiplication: * Division: / Integer division: / Modulo: % Additive inverse: -
Logical - Three or four logical operations are available, exactly how much it depends on the particular programming language that we use. with these operations, we can solve any logical task or condition. these logical conditions are for example connections of comparing values according to certain rules, testing values. logical operations are mainly used in the execution of conditional statements.
Logical and: && Logical or: || Logical negation: !
Bitwise - We have more of the bitwise operators, using the bitwise operator we can set or determine the specific bit in whole numbers.
Bitwise left shift: << Bitwise right shift: >> Bitwise and: & Bitwise or: | Bitwise not: ~ Bitwise xor: ^
Relational - The main use of the relational operators is in control of conditional statements. thanks to these, we can decide which direction to continue the conditional statements, or for example, how many iterations of the cycle need to perform.
Less than: < Greater than: > Less than or equal to: <= Greater than or equal to: >= Equal to: == Not equal to: !=
Assignment Assignment: =

Statements

Statements are important elements for writing programs. Generally one statement line corresponds to one line program. The main group of the statements are: cycles, program branching and flow control.

Expression statement: ; Block statement: { }

Java

 i = x * 5;
 while (i>0)
   if (i==10)
     break;
   else 
   {
     i--;
   }

Examples - Java

Java

 i = x * 5;
 while (i>0)
   if (i==10)
     break;
   else 
   {
     i--;
   }

Java

i & j
0xabcd & k
2 & (i & 4)

Java

Other pieces of example codes:

if (i==10)
     break;
   else 
   {
     i--;
   }

~ 2

70 / 8

x = 1.234

(float)i

xmin = -32768

Programming languages