Java Q&A
by Oliver Goldman


Listing One
     // Strategy: Suppress

     // Initialization for a class that has nothing to do with I/O
     public void initialize() {
          try {
               // Load pre-computed values for this class.
               InputStream is = new FileInputStream( CACHE_FILE );
               is.read( cache );
               ...
          } catch( IOException ex ) {
               // Ignore: donít know what to do about this error, and
               // signature doesnít allow it to propagate.
          }
     }

Listing Two
// Strategy: Bail Out

     // Initialization for a class that has nothing to do with I/O
     public void initialize() {
          try {
               // Load pre-computed values for this class.
               InputStream is = new FileInputStream( CACHE_FILE );
               is.read( cache );
               ...
          } catch( IOException ex ) {
               // After all, isnít this why printStackTrace() exists?
               ex.printStackTrace();
               System.exit( 1 );
          }
     }
Listing Three
     // Strategy: Propagate

     // Initialization for a class that has nothing to do with I/O
     public void initialize() throws IOException {
          // Load pre-computed values for this class.
          InputStream is = new FileInputStream( CACHE_FILE );
          is.read( cache );
          ...
     }
Listing Four
     // Strategy: Base Case

     // Initialization for a class that has nothing to do with I/O
     public void initialize() throws Exception {
          // Load pre-computed values for this class.
          InputStream is = new FileInputStream( CACHE_FILE );
          is.read( cache );
          ...
     }
Listing Five
     // Strategy: Wrap

     // Initialization for a class that has nothing to do with I/O
     public void initialize() throws MyAPIException {
          // Load pre-computed values for this class.
          try {
               InputStream is = new FileInputStream( CACHE_FILE );
               is.read( cache );
          } catch( IOException ex ) {
               throw new MyAPIException( "Loading cache failed", ex );
          }
          ...
     }
Listing Six
     // Unwrapping by error code
     try {
          ...
     } catch( SQLException ex ) {
          // Big Ugly Switch Statements != Object Oriented Programming.
          switch( ex.getErrorCode()) {
               case 1:
                    ...
               default:
                    // Throw an exception, perhaps?
          }
     }
     ...
Listing Seven
     // Recursively unwrapping

     try {
          ...
     } catch( MyAPIException ex ) {
          try {
               Throwable t = ex;
               while( ex != null ) {
                    t = ex.getWrappedException();
                    ex = ( t instanceof MyAPIException ? (MyAPIException) t :
null );
               }
               throw t;
          }
          catch( UnderlyingException e ) { // according to the underlying
exception type
               ...
          }
          ...
     }
Listing Eight
     public static void main( String[] args ) {
          try {
               if( args.length < 1 ) {
                    System.out.println( "usage: do [it]" );
                    System.exit( 1 );
               }
          } catch( IOException ex ) {
               // System.out isnít working, so printStackTrace() isnít any good.
               System.exit( 1 );
          }
          ...
     }
Listing Nine
     public static void main( String[] args ) {
          ...
          System.out.print( "Current progress: " );
          if( System.out.checkError()) {
               // Canít communicate with the user anymore
               System.exit( 1 );
          }
          ...
     }
}
Listing Ten
     // Unchecked exceptions

     // Initialization for a class that has nothing to do with I/O
     public void initialize() {
          // Load pre-computed values for this class.
          InputStream is = new FileInputStream( CACHE_FILE );
          is.read( cache );
          ...
     }