Exception Handling - Beginning Java 8 Fundamentals - page 342

All exceptions that are not checked exceptions are called unchecked exceptions. The Error class, all subclasses
of the Error class, the RuntimeException class, and all its subclasses are unchecked exceptions. They are called
unchecked exceptions because the compiler does not check if they are handled in the code. However, you are free to
handle them. The program structure for handling a checked or an unchecked exception is the same. The difference
between them is in the way the compiler forces (or does not force) you to handle them in the code.
Let's fix the compiler error for the ReadInput class. Now you know that java.io.IOException is a checked
exception and the compiler will force you to handle it. You will handle it by using a try-catch block. Listing 9-3 shows
the code for the ReadInput class. This time, you have handled the IOException in its readChar() method and the code
will compile fine.
Listing 9-3. A ReadInput Class Whose readChar() Method Reads One Character from the Standard Input
// ReadInput.java
package com.jdojo.exception;
import java.io.IOException;
public class ReadInput {
public static char readChar() {
char c = '\u0000';
int input = 0;
try {
input = System.in.read();
if (input != -1) {
c = (char)input;
}
}
catch (IOException e) {
System.out.print("IOException occurred while reading input.");
}
return c;
}
}
How do you use the ReadInput class? You can use it the same way you use other classes in Java. You need to call
the ReadInput.readChar() static method if you want to capture the first character entered by the user. Listing 9-4
has code that shows how to use the ReadInput class. It prompts the user to enter some text. The first character of the
entered text is shown on the standard output.
Listing 9-4. A Program to Test the ReadInput Class
// ReadInputTest.java
package com.jdojo.exception;
public class ReadInputTest {
public static void main(String[] args) {
System.out.print("Enter some text and press Enter key: ");
char c = ReadInput.readChar();
System.out.println("First character you entered is: " + c);
}
}