What is the use of collections in java? How it is
implemented in real time applications?
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Answer Posted / pradip mishra(b-tech it)
interfaces, implementations, and algorithms — that comprise
the Java Collections Framework.
General-purpose implementations are the most commonly used
implementations, designed for everyday use. They are
summarized in the table below.
Special-purpose implementations are designed for use in
special situations and display nonstandard performance
characteristics, usage restrictions, or behavior.
Concurrent implementations are designed to support high
concurrency, typically at the expense of single-threaded
performance. These implementations are part of the
java.util.concurrent package.
Wrapper implementations are used in combination with other
types of implementations, often the general-purpose ones,
to provide added or restricted functionality.
Convenience implementations are mini-implementations,
typically made available via static factory methods, that
provide convenient, efficient alternatives to general-
purpose implementations for special collections (for
example, singleton sets).
Abstract implementations are skeletal implementations that
facilitate the construction of custom implementations —
described later in the Custom Collection Implementations
section. An advanced topic, it's not particularly
difficult, but relatively few people will need to do it.
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Question 5 [15] Consider the following classes, illustrating the Strategy design pattern: import java.awt.*; abstract class Text { protected TextApplet tA; protected Text(TextApplet tApplet) { tA = tApplet; } abstract public void draw(Graphics g); } class PlainText extends Text { protected PlainText(TextApplet tApplet) { super(tApplet); } public void draw(Graphics g) { g.setColor(tA.getColor()); g.setFont(new Font("Sans-serif", Font.PLAIN, 12)); g.drawString(tA.getText(), 20, 20); } } class CodeText extends Text { protected CodeText(TextApplet tApplet) { super(tApplet); } public void draw(Graphics g) { g.setColor(tA.getColor()); g.setFont(new Font("Monospaced", Font.PLAIN, 12)); g.drawString(tA.getText(), 20, 20); } } public class TextApplet extends java.applet.Applet { protected Text text; protected String textVal; protected Color color; public String getText() { return textVal; } public Color getColor() { return color; } public void init() { textVal = getParameter("text"); String textStyle = getParameter("style"); String textColor = getParameter("color"); if (textStyle == "code") text = new CodeText(this); else text = new PlainText(this); if (textColor == "red") color = Color.RED; else if (textColor == "blue") color = Color.BLUE; else color = Color.BLACK; } public void paint(Graphics g) { text.draw(g); 10 } } The Text class is more complicated than it should be (there is too much coupling between the Text and TextApplet classes). By getting rid of the reference to a TextApplet object in the Text class and setting the colour in the paint() method, one could turn the Text class into an interface and simplify the strategy classes considerably. 5.1 Rewrite the Text and PlainText classes to do what is described above. (6) 5.2 Explain the consequent changes that are necessary to the TextApplet class. (4) 5.3 Write an additional strategy class called FancyText (to go with your simplified strategy classes) to allow fancy text to be displayed for the value "fancy" provided for the style parameter. It should use the font Font ("Serif", Font.ITALIC, 12). (3) 5.4 Explain what changes are necessary to the TextApplet class for this. (2)
What is the constructor?
