Java Reference
In-Depth Information
try
{
If an exception occurs in the
try
block,
then control transfers immediately to the
catch
block and the code in the
catch
block
is executed.
...
}
catch(Exception e)
{
...
}⇒
try
{
...
}
finally
{
...
}⇒
The code in the
finally
block is always executed.
Exception that occurs when the user enters the wrong
type. For example, the program expects an integer and the user enters a double.
⇒
InputMismatchException
Exception that occurs when the user accesses
an index of an array that is outside the elements of the array.
⇒
ArrayIndexOutOfBoundsException
ArithmeticException
An exception that occurs as a result of arithmetic opera-
tions, for example, division by 0.
⇒
⇒
FileNotFoundException
An exception that occurs when the program tries to open
a file that does not exist.
Exception
⇒
The main exception class. All other exception classes inherit from it.
throw new Exception("
...
")
⇒
Creates and throws a new exception.
e.printStackTrace();
⇒
Prints the stack trace when the
e
exception occurs, that
is, the order of methods that were called.
try(open a file)
{
Opens a file. If an ex-
ception occurs, then control jumps over to the
catch
block. The file is closed auto-
matically at the end.
...
}
catch(Exception e)
{
...
}⇒
if (fileChooser.showDialog(..., "Open") == JFileChooser.APPROVE OPTION)
{
Shows a file chooser dialog. The missing parameter is a reference to the par-
ent window.
...
}⇒
⇒
Gets a file object from a file
File newFile = fileChooser.getSelectedFile();
chooser.
Scanner inFile = new Scanner(file);
⇒
Creates a
Scanner
object from a file.
String s = inFile.nextLine();
⇒
Reads a line from a file.
⇒
String n = inFile.nextInt();
Reads an integer from a file.
⇒
True if there is a next line in the file.
inFile.hasNextLine()
inFile.hasNextInt()
⇒
True if there is a next integer in the file.
inFile.close()
⇒
Closes the file.
File newFile = new File("myFile.txt");
⇒
Creates an object of type
File
by
opening the file
myFile.txt
.
PrintWriter fileWriter = new PrintWriter("myFile.txt");
⇒
Creates an ob-
ject of type
PrintWriter
.
fileWriter.print("hello");
⇒
Prints hello to the file.
⇒
Closes the file.
fileWriter.close();
