What are the best practices for exception handling in Java?

• Catch specific exceptions, not just Exception or Throwable.
• Never swallow an exception with an empty catch. At least log it.
• Use try with resources to close files, sockets and connections.
• Keep the cause when you wrap an exception: throw new MyException("message", e).
• Add useful details to the message: which value, which file.
• Do not use exceptions for normal flow, like ending a loop. They are slow and unclear.
• Throw early, catch late: check arguments at the start, and handle the error where you can do something about it.
• Use unchecked exceptions for programming errors, and checked ones only when the caller can recover.

public class Main {
    static class ConfigException extends RuntimeException {
        ConfigException(String message, Throwable cause) { super(message, cause); }
    }

    static int readPort(String text) {
        try {
            return Integer.parseInt(text);
        } catch (NumberFormatException e) {
            throw new ConfigException("Invalid port value '" + text + "'", e);    // keeps the cause
        }
    }

    public static void main(String[] args) {
        try {
            readPort("80x");
        } catch (ConfigException e) {
            System.out.println(e.getMessage());
            System.out.println("Cause: " + e.getCause());
        }
    }
}

See Java Exceptions.

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