🏷 Exception Handling
5 patterns
Topic: Exception Handling
All Java patterns related to Exception Handling — java.evolved
I/O
Try-with-resources improvement
Old
Connection conn = getConnection();
// Must re-declare in try
try (Connection c = conn) {
use(c);
}
Modern
Connection conn = getConnection();
// Use existing variable directly
try (conn) {
use(conn);
}
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JDK 9+
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Errors
Helpful NullPointerExceptions
Old
// Old NPE message:
// "NullPointerException"
// at MyApp.main(MyApp.java:42)
// Which variable was null?!
Modern
// Modern NPE message:
// Cannot invoke "String.length()"
// because "user.address().city()"
// is null
// Exact variable identified!
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JDK 14+
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Errors
Multi-catch exception handling
Old
try {
process();
} catch (IOException e) {
log(e);
} catch (SQLException e) {
log(e);
} catch (ParseException e) {
log(e);
}
Modern
try {
process();
} catch (IOException
| SQLException
| ParseException e) {
log(e);
}
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JDK 7+
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Errors
Optional.orElseThrow() without supplier
Old
// Risky: get() throws if empty, no clear intent
String value = optional.get();
// Verbose: supplier just for NoSuchElementException
String value = optional
.orElseThrow(NoSuchElementException::new);
Modern
// Clear intent: throws NoSuchElementException if empty
String value = optional.orElseThrow();
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JDK 10+
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Tooling
Class.newInstance() to constructor reflection
Old
Plugin plugin = pluginClass.newInstance();
Modern
Plugin plugin = pluginClass
.getDeclaredConstructor()
.newInstance();
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JDK 9+
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