This page examines the differences in how programming languages detect and intercept events that disrupt the normal flow of a program's execution.
VB error handling is limited to On Error GoTo statements.
To issue exceptions the code cannot intercept on its own (such as data in the wrong format). It must first create an instance of java.lang.Throwable, then declare the signature of a method with a throws clause with throw objects.
Subclasses can declare subclasses of the class declared. For example, EOFException (End of File Exception) is a subclass of IOException.
Among the 50+ subclasses generated by the Java runtime system's Java Exception Classes are:
Java developers write throw objects under the Exception subclass derived from the java.lang.Thowable interface. This Throwable class is the superclass of all errors and exceptions in the Java language. Only objects that are instances of this class (or one of its subclasses) are (can be) thrown by the throw statement. Similarly, only this class or one of its subclasses can be the argument type in a catch clause.
java.lang.Error subclasses (such as the VirtualMachineError subclass thrown by the JVM) are not recoverable. Errors arise when Events external to a program code occur, such as the JVM running out of memory, cause program code to stop.
Checked?An exception is "checked" if the compiler checks whether coding exists to anticipate/handle that exception.
All classes are checked by the compiler except for java.lang.RuntimeException and Error subclasses, which are unchecked by the compiler.
The Error subclass of the Throwable class is a sibling class of the Exception subclass. In other words, the compiler does not require coding to declare or catch Exception Errors.
For example, when trying the Thread.wait() method, the code should include a catch for InterruptException.
The JRE terminates with a NullPointerException if it can't find an appropriate catch somewhere up the call stack.
A variable referenced in try or catch blocks must be declared before entering the try block.
Exception handling in German is Ausnahmebehandlung.
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