Java try/catch - finally usefulness

Question

I never use it so I'm wondering about the usefulness of the finally block.

What's the difference between

try {
    // A
} catch(...) {
    // B
} finally {
    // C
}

and

try {
    // A
} catch(...) {
    // B
}
// C

In both cases :

if no exceptions -> A,C

if exceptions -> A,B,C

[Read This...](https://www.javatpoint.com/finally-block-in-exception-handling#:~:text=Java%20finally%20block%20is%20a,the%20exception%20occurs%20or%20not.). — DevilsHnd - 退職した, Jan 25 '23 at 08:48

score 1 · Answer 1 · answered Jan 25 '23 at 08:47

1

There will be a difference if A throws an exception not caught in catch or if the catch block throws an exception.

answered Jan 25 '23 at 08:47

Adam Siemion

15,569
7
58
92

score -2 · Answer 2 · answered Jan 25 '23 at 09:02

-2

Can be used to close/free resource after exception has occurred. Example java function bellow.

public static ArrayList foo(Connection conn) throws SQLException {
    ArrayList results = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    try {   
        // create a query, perform the query and
        // process the results
    } finally {
        try {
             rs.close();
        } catch(SQLException ex) {
            throw new RuntimeException(ex);
        }
        try {
            ps.close();
       } catch(SQLException ex) {
           throw new RuntimeException(ex);
       }
    }
    return results;
}

answered Jan 25 '23 at 09:02

Dennis Earlyman

69
1
6

ever heard of try-with-resources? – Sören Jan 25 '23 at 09:24
couldn't get appropriate term to use, I meant things like I/O tasks – Dennis Earlyman Jan 26 '23 at 10:40
Use try-with-resources. Btw, your code is broken. ps.close() is never called, when rs.close() throws an exception. – Sören Jan 26 '23 at 10:56

Java try/catch - finally usefulness

2 Answers2