Exception

• An Exception indicates conditions that a reasonable application might want to catch.
• An Error indicates serious problem that a reasonable application should not try to catch:StackOverflowError, Both Error and Exceptions extend from Throwable

Checked Exception

• Exceptions other than Runtime Exception. Must use either try/ catch block or throws

try {
    FileInputStream fs = new FileInputStream("./a.txt");
} catch (FileNotFoundException e) {
    System.out.println("catch...");
    e.printStackTrace();
} finally {
    System.out.println("finnaly...");
}

// leave it to JVM
public class ExceptionTest {
    public static void execute() throws Exception {
        System.out.println("execute...");
        throw new Exception();
    }

    public static void main(String[] args) throws Exception {
        execute();
    }
}

• Multiple catch: Subclass must be before superclass

New forms in Java 7

• Try with resources

和python里 “with open() as f:” 一样

static String readFirstLineFromFile(String path) throws IOException {
    try (BufferedReader bt = new BufferedReader(new FileReader(path))) {
        return br.readLine();
    }
}

catch (IOException | SQLException) {
    logger.log(ex);
    throw ex;
}
// duplicated code elimitated!