Ejemplo

public static void main(String[] args){
int version = 6;
String applicaiton = "Rational Developer "; //$NON-NLS-1$

String edition = "para Java "; //$NON-NLS-1$
String message = "Esta es la versión"; //$NON-NLS-1$
message = message.concat(String.valueOf(version));
message = message.concat(" de "); //$NON-NLS-1$
message = message.concat(applicaiton);
message = message.concat(edition);
message = message.concat("\"."); //$NON-NLS-1$
System.out.println(message);
}
Solución
Utilice java.text.MessageFormat para formatear mensajes.

public static void main(String[] args){
final String MSG_FORMATSTRING="Rational Developer {0} versión {1}"; //$NON-NLS-1$
final String VERSION = "versión"; //$NON-NLS-1$
final String EDITION = "edición"; //$NON-NLS-1$
final String JAVA = "para Java"; //$NON-NLS-1$
final String MY_RESOURCES = "MyResources"; //$NON-NLS-1$

ResourceBundle myResources = ResourceBundle.getBundle(MY_RESOURCES, Locale.US );
String version = myResources.getString(VERSION);
String edition = myResources.getString(EDITION);

MessageFormat form = new MessageFormat(MSG_FORMATSTRING);
Object[] testArgs = {new Integer(6), JAVA};
System.out.println(form.format(testArgs));
}