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    Java JDK and Intro

    Uploaded by

    Thene Truthe Nowe
    This document provides an overview of key Java concepts such as variables, data types, conditional statements, loops, methods, arrays, and classes. It explains that Java programs begin with a class that matches the file name, and provides a "Hello World" example. Integer variable types like byte, short, int, and long are described along with floating-point types like float and double. Conditional statements like if-else and switch are covered as well as different loop types including while, do-while, and for loops. The document also discusses methods, overloading methods, and overriding methods. Finally, it explains how to declare and access elements in both single and multi-dimensional arrays.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Java JDK and Intro

    Uploaded by

    Thene Truthe Nowe
    11 views39 pages
    This document provides an overview of key Java concepts such as variables, data types, conditional statements, loops, methods, arrays, and classes. It explains that Java programs begin with a class that matches the file name, and provides a "Hello World" example. Integer variable types like byte, short, int, and long are described along with floating-point types like float and double. Conditional statements like if-else and switch are covered as well as different loop types including while, do-while, and for loops. The document also discusses methods, overloading methods, and overriding methods. Finally, it explains how to declare and access elements in both single and multi-dimensional arrays.

    Original Description:

    Java introduction and pratice

    Original Title

    JAVA JDK AND INTRO

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    © © All Rights Reserved

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    This document provides an overview of key Java concepts such as variables, data types, conditional statements, loops, methods, arrays, and classes. It explains that Java programs begin with a class that matches the file name, and provides a "Hello World" example. Integer variable types like byte, short, int, and long are described along with floating-point types like float and double. Conditional statements like if-else and switch are covered as well as different loop types including while, do-while, and for loops. The document also discusses methods, overloading methods, and overriding methods. Finally, it explains how to declare and access elements in both single and multi-dimensional arrays.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    11 views39 pages

    Java JDK and Intro

    Uploaded by

    Thene Truthe Nowe
    This document provides an overview of key Java concepts such as variables, data types, conditional statements, loops, methods, arrays, and classes. It explains that Java programs begin with a class that matches the file name, and provides a "Hello World" example. Integer variable types like byte, short, int, and long are described along with floating-point types like float and double. Conditional statements like if-else and switch are covered as well as different loop types including while, do-while, and for loops. The document also discusses methods, overloading methods, and overriding methods. Finally, it explains how to declare and access elements in both single and multi-dimensional arrays.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 39

    First of all you need to download and install your java JDK to compile and run the codes

    JDK= Software Development Kit

    https://www.oracle.com/br/java/technologies/javase-downloads.html
    Follow the steps(MAC or Windows) to install your java JDK.
    Java is a programming language.
    Java Tutorial Java is used to develop mobile apps, web apps,
    desktop apps, games and much more.
    Java Quickstart
    In Java, every application begins with a class name, and that class must match the filename.
    Let's create our first Java file, called P1_Hello.java, which can be done in any text editor (like
    Notepad).
    The file should contain a "Hello World" message, which is written with the following code:

    Note: Java is
    case-
    sensitive:
    "MyClass"
    and
    "myclass"
    has different
    meaning.
    Java Identifiers
    All Java variables must be identified with unique names.
    These unique names are called identifiers.
    Identifiers can be short names (like x and y) or more descriptive names (age, sum,
    totalVolume).
    Note: It is recommended to use descriptive names in order to create understandable
    and maintainable code:
    Integer Types
    Byte
    The byte data type can store whole numbers from -128 to 127. This can be used instead of int or other integer
    types to save memory when you are certain that the value will be within -128 and 127:

    Example
    byte myNum = 100;
    System.out.println(myNum);

    Short
    The short data type can store whole numbers from -32768 to 32767:
    Example
    short myNum = 5000;
    System.out.println(myNum);

    Int
    The int data type can store whole numbers from -2147483648 to 2147483647. In general, and in our
    tutorial, the int data type is the preferred data type when we create variables with a numeric value.
    Example
    int myNum = 100000;
    System.out.println(myNum);
    Long
    The long data type can store whole numbers from -9223372036854775808 to
    9223372036854775807. This is used when int is not large enough to store the value. Note that
    you should end the value with an "L":
    Example
    long myNum = 15000000000L;
    System.out.println(myNum);

    Float
    The float data type can store fractional numbers from 3.4e−038 to 3.4e+038. Note that you
    should end the value with an "f":
    Example
    float myNum = 5.75f;
    System.out.println(myNum);

    The double data type can store fractional numbers from 1.7e−308 to 1.7e+308. Note
    that you should end the value with a "d":
    Example
    double myNum = 19.99d;
    System.out.println(myNum);
    Booleans
    A boolean data type is declared with the boolean keyword and can
    only take the values true or false:
    Example
    boolean isJavaFun = true;
    boolean isFishTasty = false;
    System.out.println(isJavaFun); // Outputs true
    System.out.println(isFishTasty); // Outputs false
    Use the else statement to specify a block of code to be executed if the condition is false.
    The else if Statement
    Use the else if statement to specify a new condition if the first condition is false.
    Java Switch Statements
    Use the switch statement to select one of many code blocks to be executed.
    Loops
    Loops can execute a block of code as long as a specified condition is reached.
    Loops are handy because they save time, reduce errors, and they make code more readable.

    Java While Loop


    The while loop loops through a block of code as long as a
    specified condition is true:

    The Do/While Loop


    The do/while loop is a variant of the while loop. This
    loop will execute the code block once, before checking if
    the condition is true, then it will repeat the loop as long
    as the condition is true.
    Statement 1 is executed (one time) before the execution of the code block.
    Statement 2 defines the condition for executing the code block.
    Statement 3 is executed (every time) after the code block has been executed.
    The example below will print the numbers 0 to 4:
    For-Each Loop
    There is also a "for-each" loop, which is
    used exclusively to loop through
    elements in an array:
    Method Overloading
    With method overloading, multiple methods can
    have the same name with different parameters:
    Overriding in Java
    In any object-oriented
    programming language,
    Overriding is a feature that
    allows a subclass or child
    class to provide a specific
    implementation of a
    method that is already
    provided by one of its
    super-classes or parent
    classes. When a method in
    a subclass has the same
    name, same parameters or
    signature, and same
    return type(or sub-type)
    as a method in its super-
    class, then the method in
    the subclass is said
    to override the method in
    the super-class.
    Java Arrays
    Arrays are used to store multiple values in a single variable, instead of declaring
    separate variables for each value.
    To declare an array, define the variable type with square brackets:
    String[] cars;

    Access the Elements of an Array


    You access an array element by referring to the index
    number.
    This statement accesses the value of the first element
    in cars:

    Change an Array Element


    To change the value of a specific
    element, refer to the index number:
    Array Length
    To find out how many elements an array has, use the length property:

    Loop Through an Array


    You can loop through the array elements with the for loop, and use
    the length property to specify how many times the loop should run.
    The following example outputs all elements in the cars array:
    Loop Through an Array with For-Each
    There is also a "for-each" loop, which is used
    exclusively to loop through elements in arrays:
    We can also use a for loop inside another for loop to get the elements of
    a two-dimensional array (we still have to point to the two indexes):
    Example

    public class Main {


    public static void main(String[] args) {
    int[][] myNumbers = { {1, 2, 3, 4}, {5, 6, 7} };
    for (int i = 0; i < myNumbers.length; ++i)
    {
    for(int j = 0; j < myNumbers[i].length; ++j) {
    System.out.println(myNumbers[i][j]); }
    }

    } }
    End

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