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MySQL Java Connection Reading data from the keyboard with Java (fourth form)

Along with the version of Java 5 came a new set of classes, including one that allows us to read data from the keyboard even easier than previously seen classes.

Scanner class of java.util package which gives us the ability to process data entered from the keyboard under primitive type they belong to these entries. This is achieved by treating the input data as tokens of an expression separated by a boundary that we have specified.

Let's see an example of the above ...

turns out that we need to write a Java program that allows capturing personal data of a company's payroll. We read data such as name, address, age and salary of an employee. We know the names that will introduce the program String class, like directions. While the employee's age must be an integer value and the wage is given in numbers with decimals. In short:

String name = "";

String address = "";

int age = 0;

double salary = 0.0;

Earlier we saw that the class BufferedReader capture data allowed keyboard through method readLine () , which returns a value type we String would subsequently be converted to numeric processing. However, the class Scanner contains specific methods for reading data much faster and safer, but above all, without the need for conversions ourselves. Following is a summary of these methods:

constructor Summary:

Scanner (File file)

Creates a new Scanner that produces values \u200b\u200bfrom a specified file.

Scanner (InputStream inputStream)

Creates a new Scanner that produces values \u200b\u200bfrom an input stream of data.

Scanner (String source)

Creates a new scanner from a particular string.

Summary of methods:

void close () Closes

Pattern Scanner delimiter () Returns

Scanner delimiter pattern

findInLine String (Pattern pattern)

Try searching a string in the scanner to ignore the patterns

boolean hasNext ()

Returns true if the value contains more tokens Scanner

boolean hasNext (String pattern )

Returns a true value if the Scanner contains the specified pattern

nextBoolean boolean ()

Scans the next token of the input to a Boolean value and returns that value.

nextByte byte ()

Scans the next token of the input as a byte.

double nextDouble ()

Scans the next token of the input as a double. Float

nextFloat ()

Scans the next token of the input as a float.

int nextInt ()

Scans the next token of the input as an int. String

nextLine () Returns

entire current line.

long nextLong ()

Scans the next token of the input as a long.

short nextShort ()

Scans the next token of the input as a short.

Then, with the Scanner class can perform data reads to solve our example.

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Reading data from the keyboard in Java (Third form) responds to events

In the previous post on reading data from the second form use a method that returns the text we put into a command prompt / terminal until you press the enter key , or which is equal to that System.in receive '\\ n' (line using the backslash caractetes). The data that we receive the added to a string that is returned upon completion with the reading method. One way to perform the above process is helping us with a read buffer. Buffer to be defined as the space in the memory of our computer that we can store a certain amount of information temporarily or until they are processed.

class from java.io BufferedReader is a class that allows us to read data in sequence, which gives us greater reliability in the reading done. By default, the buffer created BufferedReader is large enough to cover virtually any need, and also gives us the possibility to obtain the text from a file or other information flow.

To read data from our console have to wrap within BufferedReader data flow manipulate them in our case we will use the keyboard to the class to wrap InputStreamReader also java.io package , a bridge between the standard input buffer and Java, as InputStreamReader is a decoder bytes causes us these bytes in the corresponding character. So it is strongly recommended to use the buffer for reading data. However, suffice to specify where to get the InputStreamReader to convert bytes to characters.

Some methods of the class BufferedReader are void

close () - Close reading of data flow Void

mark (int anchor) - Mark the position in the data stream int

read () - Read a single character String

readLine ( ) - Read a line of text

ready boolean () - Decide if the flow is ready to be read

void reset () - Restores flow to the brand
recent
Example:

{public class

Reading Public static void main (String args []) {

String name = "" , address = ", phone = " " ;

BufferedReader buffer = new BufferedReader ( new InputStreamReader (System.in));

System . out. Print ( Name: ")

name = buffer. readLine ();

System.out. print ( "Address:" )

address = buffer. readLine ();

System.out. print ( "Telefono: ")

phone = buffer. readLine ();
System.out. println ( "\\ nData enter: \\ n" + name + "\\ n" + address + "\\ n" + phone);

System. exit (0);

}}

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JTextField Reading

At the request of my friend Pollitux talk about events that produce the keyboard on a JTextField to process data quickly on this component.

class JTextField javax.swing package is a class that helps us to create text boxes, graphical user interfaces, which can be adding in a form and ask the user for a value we need to processing such as name, age, address, email, etc. Like all elements have a lot of methods and I shall only discuss some methods relevant.

Builders:

JTextField () - Creates an empty text field.

JTextField (int columns) - Creates an empty text field with a specific number of columns.

JTextField (String text) - Create a text field with a message

JTextField (String text, int columns) - Create a text field with a message and a specific number of columns.

Methods:

Void

addActionListener (java.awt.event.ActionListener action)

Adds a listener component action events, there is generally when we enter into the text field.

void addKeyListener (java.awt.event.KeyListener eventoTeclado)

Adds a listener component events from the keyboard, including enter. Responds to events like pressing a key, and release a key when painting the character corresponding to the key in the text field.

void addMouseListener (java.awt.event.MouseListener eventoMouse)

A gregarious an event listener component generated by the mouse.

void setFont (java.awat.Font source) - I change the font for the text field.

Our focus is on the KeyListener interface. This class provides three methods that we implement and are responding to keyboard events mentioned above:

void keyPressed (KeyEvent evt) - This method is invoked when a key is pressed.

void keyReleased (KeyEvent evt) - This method is invoked when a key is released.

void keyTyped (KeyEvent evt) - This method is invoked when the character is printed for the key pressed on a text field.

NOTE: As KeyListener is an interface must implement all methods, however, if we do not need all the adapters to use the listening component. All interfaces of action have an adapter that helps us to implement only the methods we need, if we may use your class KeyListener adapted KeyAdapter call.

Here a small example of using the KeyListener interface:

java.awt.GridLayout import, import
java.awt.event.KeyListener;
import java.awt.event . KeyEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField ;

EventosTeclado public class extends JFrame implements KeyListener {

    public EventosTeclado () {
        super ( "La interface KeyListener" );
        setSize ( 400, 150 );
        setLocationRelativeTo ( null );
        setResizable ( false );
        setDefaultCloseOperation ( JFrame. EXIT_ON_CLOSE );
        iniciarGUI ();
    }

    private void iniciarGUI () {
        JPanel pnlCampos = new JPanel ( new GridLayout ( 3, 2, -100, 0 ) );
        pnlCampos. setBounds ( 10, 10, 380, 85 );
        cmpNumero1 = new JTextField ( "0" );
        cmpNumero1. addKeyListener ( this );
        cmpNumero2 = new JTextField ( "0" );
        cmpNumero2. addKeyListener ( this );
        cmpResultado = new JTextField ( "0" );
        pnlCampos. add (new JLabel ( "Number:" ));
pnlCampos. add (cmpNumero1);
pnlCampos. add (new JLabel ( "Number:" ));
pnlCampos. add (cmpNumero2);
pnlCampos. add ( new JLabel ( "Sum:" ));
pnlCampos. add (cmpResultado)
getContentPane (). setLayout (null )
getContentPane (). add (pnlCampos)
}

public void keyPressed (KeyEvent AD) {
Sumar ();
}

public void keyReleased (KeyEvent AD) {
Sumar ();}


public void keyTyped (KeyEvent evt) {
summer ();}



private void summer () {
double amount = 0;
try {
; = double the amount. parseDouble (cmpNumero1. gettext ()) + double. parseDouble (cmpNumero2. gettext ());}

catch (NumberFormatException exc) {
sum = 0;

} finally {
; cmpResultado. setText ( "" + suma );
        }
    }

    public static void main ( String args[] ) {
        new EventosTeclado (). setVisible ( true );
   
}

private JTextField cmpNumero1;
private JTextField cmpNumero2;
private JTextField cmpResultado;
}