class CustomException extends Exception

Week 5: Class hierarchies/14A. More exercises: Custom Exceptions+++

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+Let's conclude this section by discussing inheritance and OWN EXCEPTIONS.
+
+In Java, a 'new exception class' can be defined by inheriting class Exception. 
+Usually, it's enough to define a constructor which gets a message (a String) as an argument and 
+then calls the super class constructor.
+
+Consider the following example:
+class TooLongMessageException extends Exception {
+    public TooLongMessageException(String message) {
+        super(message);
+    }
+}
+ 
+Own exception can be thrown like any other exception.
+
+
+
+
+Note that a method that may throw a 'checked exception', must declare this with the 'throws' keyword. 
+This also concerns the constructor.
+
+class TextMessage {
+    private String sender;
+    private String recipient;
+    private String message;
+    
+    public TextMessage(String sender, String recipient, String message) 
+            throws TooLongMessage {
+        this.sender = sender;
+        this.recipient = recipient;
+        setMessage(message);
+    }
+
+    // METHOD 'throws' OUR OWN CUSTOM-DEFINED EXCEPTION
+    public void setMessage(String message) throws TooLongMessage {
+        if (message.length() > 160) {
+            throw new TooLongMessageException("Maximum length is 160 characters");
+        }
+        this.message = message;
+    }
+}
+ 
+
+
+
+
+An exception like this needs to be caught when the method is called:
+public static void main(String[] args) {
+    Scanner reader = new Scanner(System.in);
+    while (true) {
+        System.out.print("Give sender, empty line exits: ");
+        String sender = reader.nextLine();
+        
+        if (sender.equals("")) {
+            break;
+        }
+        
+        System.out.print("Give recipient: ");
+        String recipient = reader.nextLine();
+        
+        System.out.print("Give message: ");
+        String message = reader.nextLine();
+
+        // TRY-CATCH TO CATCH EXCEPTION 'e'
+        try {
+            TextMessage textMessage= new TextMessage(sender, recipient, message);
+        } 
+        catch (TooLongMessageException e) {
+            System.out.println("Could not create a message: " + e.getMessage());
+        }
+    }
+}
+
+
+
+
+
+
+