Programming

Front 1

Reusing constructors

Back 1

-One constructor can call other constructors.

-The use the word this as the first word for the constructor

public MyTime(int h, int m)

{ hours = h;

mins = m;

}

public MyTime(int hhmm)

{ int h = hhmm/100;

int m= hhmm%100;

this(h,m)

}

Front 2

what happens in memeory when an object is passed as a paramater to a method

Back 2

When the object is created a special space in memory is reserved for it, and the memory address is returned to the identifier. It is the memory address of the object that we pass as a parameter to a method. Which may make a new copy of the address

Front 3

find the size of an array

Back 3

array.length; it is not a method

Front 4

Default definition for whitespace

Back 4

Is space, tab, new line

Front 5

token definition

Back 5

A block of non-whitespace characters, note we can customise what we define as whitespace

Front 6

Which class would you use to write streams of characters to a file

Back 6

Use the FileWriter class

FileWriter writer = new FileWriter("MyData.txt")

The write method can be used to write a single character

char c = '?';

writer.write(c);

The file should be close after writer operations are complete

Front 7

File class; how to construct File object and what methods it has

Back 7

File f = new File("the file name");

f.exists() returns true if file exists

f.length() returns the number of bytes in a file as an int

f.delete() deletes the file

f.canRead(), f.canWrite()

f.isDirectory(), f.isFile() normal file

f.lastModified() returns the time as a long

f.setLastModified() set the modification time

f.mkdir() creates a directory (folder) with this file name

Front 8

can use the file class to create a specific file rather than a String name

Back 8

File f = new File("MyData.txt")

PrintWriter writer = new PrintWriter(f);

Front 9

When using PrintWriter, FileReader and File what must the constructors contain

Back 9

The filename in quotation marks ie "filename.txt"

Front 10

Reading Streams of raw bytes

Back 10

Use FileInputStream class

FileInputStream input = new FileInputStream("MyData.txt")

The read method returns a single byte encoded as an integer

int next = input.read() returns -1 if at end of file

If not at the end of file we can cast the integer as a byte and process the data required

b = (byte) next;

Front 11

Writing Streams of raw bytes

Back 11

Use FileOutputStream class

FileOutputStream output = new FileOutputStream("MyData.txt");

The write method can be used to write a single byte

byte b = ...;

output.write(b);

The file should e closed after write operations are complete

output.close();

Front 12

Define what a JFrame object is

Back 12

An independent window or screen

Front 13

What must we import to use JFrame

Back 13

import javax.swing.*;

Front 14

What must we import to use the ActionListener class

Back 14

import java.awt.event.*;

Front 15

What is the easiest way to get a listener object?

Back 15

-Use our JFrame object to listen for ActionEvents

-ButtonFrame must implement ActionListener as well as extend JFrame

public class ButtonFrame extends JFrame implements ActionListener

Front 16

When we are using precision in String format is decimal point included in precision

Back 16

Yes, decimal place is counted, so if we have %5.2f means fieldwidth 5, so 2 for before decimal place, 1 for decimal, and 2 after decimal

Front 17

What to import if we want to JPanel

Back 17

import java.awt.*;