Notes on core java

1. Core Java
Debasish Pratihari
Button Class
Constructor:
 public Button () Constructs a Button with no
label.
 public Button(String caption)  Constructs a
Button with label as specified by the caption
argument.
Methods :
 Sets the

public void setLabel(String label)

button lable as specified.
public String getLabel() Returns the button
label or null if no label is in the button.

public Label(String text)


Label Class
 constructs an label
with specified string
public Label( )  constructs an empty label
public Label(String text , int alignment) 
constructs a new label with specified string and
specified alignment.The alignment constants are
Label.LEFT,Label.RIGHT,Label.CENTER
Methods :
 public void setText(String text)sets the text for
the label as specified.
 public String getText( ) returns the label of the
Label.
Choice class (Combo box Control)
Constructor
 public Choice( )  creates a new Combo box with no item
Methods
 public s void add(String item)  adds an item to the
Combo
 public void addItem(String item)  adds an item to the
Combo
 public int getItemCount( ) returns the no. of
 public String getItem(int index)  returns a string at the
specified index in the choice menu
 public int getSelectedIndex( ) returns the index of the
currently selected item in the Choice menu.
 public synchronized String getSelectedItem( )  returns
a String representation of currently selected item from the
choice menu
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2. Core Java
Debasish Pratihari
TextField class
Constructor




public TextField() 
creates
public TextField(String text)
a TextField
creates a new
text field initialized with specifies text
public TextField (int columns) constructs a new
empty text field with specified no. of columns
public TextField(String text , int columns)
constructs a new text field initialized with the
specified
string and wide enough to hold the
specified string
Methods

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

public void setEchoChar(char
c)
 sets the echo
character for this text field
public char getEchoChar()  gets the echo
character for the text field
public void setColumns(int col)  sets the no. of
columns for the text field
public int getColumns( )  returns the no of
columns in the text field
public void setEditable(boolean b)  Sets the
component to be editable or not if b is true then
editable otherwise not editable.
TextArea class
Constructor :
 public TextArea( )  constructs a new text area
 public TextArea(String text)  constructs a new
text area with specified text
row ,int col)  constructs a
text area with specified no. of rows and columns

public TextArea( int

public TextArea(String

public TextArea(String text, int row , int col,, int
scrollbar)
 constructs a text area with specified
text
,int
rows ,int
cols)
 constructs a text area with specified no. of rows
and columns initializes the text specified.
text & with cols & rows and scroll bar visibility as
specified the constant for scrollbars argument are
o
o
o
o
SCROLLBARS_BOTH
SCROLLBARS_VERTICAL_ONLY
SCROLLBARS_HORIZONTAL_ONLY
SCROLLBARS_NONE
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3. Core Java
Debasish Pratihari
Checkbox class
Constructors

public Checkbox()  creates a checkbox with no

public Checkbox( String


label and state is set to “off”
label)  creates a
checkbox with the specified label as specified and
state is set to “off”
public Checkbox( String label , boolean state)
creates a checkbox with a specified label and the
state of checkbox Is as specified in the Boolean
argument, true for on state & table For “off” state.
public Checkbox(String label , boolean state ,
CheckboxGroup g) creates a checkbox with
specified label,and State as specified and combined
to a checkbox Group class

public Checkbox(String label ,CheckboxGroup
boolean state)- Same use as above.
g ,
Methods




label)  sets a label
for the check box specified
public String getLabel( )  gets the label of this
checkbox as specified
public void setState(boolean state) sets the state
of this checkbox true for “on” & false for “off”
public Boolean getState( )  returns Boolean that
represent the state of this checkbox returns true if
“on” & false is “off”
public void setLabel(String
Container class
Methods:
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public Component add(Component comp)  adds the
specified component to the container.
public Component add(Component comp, int
alignment)  adds the component and follows the
alignment as specified.
public void remove(Component comp)  removes the
specified component form the container.
public int getComponentCount() returns the no of
components in the container.
public Component[ ] getComponents() returns an
array containing the components in the container.
public void removeAll() removes all the components
from the container.
public void setLayout(LayoutManager mgr)  sets
the layout for this container.
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4. Core Java
Debasish Pratihari
Component class

public setVisible (boolean b)  if b is true then shows
the component otherwise hide it.

public void setSize(int width, int height)  resizes
the component to the specified size.

public void setBounds(int x, int y, int width, int
height)  moves the component to the corresponding
width and height.

public void setLocation(int x, int y)  Moves this
component to new location.

public void setName (String name)  Sets the name
of the component to the specified string.

public String getName() Returns a String object
representing the component name.

public void setForeground(Color c)  Sets the
foreground color to the component.

public Color getForeground () Returns the Color
object specifying the color of the component.

public void setFont (Font f) Sets the font for the
component name.

public Font getFont() Returns the font of this
component.

publilc void setEnable(boolean b)  Enables/disables
the component if b is true/false.

public boolean isEnable() Returns true if the
component is enable otherwise false.

public void setCursor(Cursor c)  Sets the cursor to
the component.

public Cursor getCursor() Returns the cursor set for
this component.

public void setBackground(Color c)  Sets the
background color for component.

public Color getBackground() Returns the color
object specifying the color set for the component.

public void repaint() Repaints the component.

public void add(PopupMenu popup)  adds a popup
menu for the component.

public void remove(PopupMenu popup)  Removes
the particular popup menu from the component.

public void Paint(Graphics g)  paints the component
to use this we need to override the method.
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5. Core Java
Debasish Pratihari
Frame class
Constructor
 public Frame( )creates a new invisible frame .
 public Frame(String title)creates a new frame with
title as specified.
Methods
 public void setTitle(String title) sets the title of the
frame
 public String getTitle( )returns the title of the frame.
 public void setResizable(boolean resize)sets the
resizeable flag which determines whether this frame is
resizable or not.
 public boolean isResizable()returns true if the frame
is resizable or not.
 public void setMenuBar(MenuBar mb)sets the
menu bar for this frame.
 public MenuBar getMenuBar( )returns the menu bar
for this frame or null if frame doesnot have any menu bar.
 public void remove(MenuComponent m)removes
the specified menu bar from this frame.
 public setCursor(int cursoe_type)sets the cursor
for the frame
Dialog class
Constuctors:
 public Dialog(Frame parent)creates an invisible
dialog with empty title.
 public Dialog(Frame parent ,boolean
modal)creates an invisible dialog with an empty title
and modal depending on modal=true/false.
 public Dialog(Frame parent , String title)constructs
an invisible dialog with specified title.
 public Dialog(Frame parent , String title , boolean
modal)constructs an invisible dialog with specified title
and modal state with specified mode=true/false value.
Methods:
 public void setModal(boolean b)sets the dialog as
modalif bis true otherwise not.
 public boolean isModal()returns true if the dialog is
modal dialog.
 public void setTitle(String title)sets the title of the
dialog.
 public void setResizable(boolean b)if b=true then
the dialog box is set to resizable otherwise not.
 public boolean isResizable( )returns true if it is
resizable.
 public String getTitle( )returns the title of the dialog.
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6. Core Java
Debasish Pratihari
FileDialog class
Constructors:

public FileDialog(Frame parent)creates a file dialog
for loading a file with an empty title.

public FileDialog(Frame parent , String
title)creates a file dialog with a specified title for
loading a file ,the files are shown in the current directory

public FileDialog(Frame parent,String title,int
mode)create a file dialog with specified title for loading
and saving a file if the value of mode=LOAD the file
dialog is finding a file to read, if mode=SAVE then file
dialog is finding a place to write a file.
Methods:

public String getDirectory( )gets the directory for
this file dialog

public void setDirectory(String
dir)sets the
directory of this file dialog to be the specified directory.

public String getFile( )returns the currently selected
file of the file dialog or null if no file is selected.

public void setFile(String file)sets the selected file
for the file dialog to be the specified file.

public int getMode()indicates whether the file dialog
is for loading or saving.

public void setMode(int mode)sets the mode
mode=FileDialog.LOAD or FileDialog.SAVE
Panel class
Constructors:

public Panel()creates a new panel using default
layout manager.the default layout is FlowLayout.

public Panel(LayoutManager mgr)creates a new
panel with specified layout manager.
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