Introduction to Programming Languages/Catching exceptions

Try-Catch The main exception handling mechanism is:try { ... } catch (...) { ... } Intuition Behind try The:tryblock means: “Try to execute this”. The:catchblock means: “If a certain error occurs, handle it here”. Example try { int i = Integer.parseInt(args[0]); int j = Integer.parseInt(args[1]); System.out.println(i / j); } catch (ArithmeticException a) { System.out.println("You are dividing by zero!"); } Execution Flow Normal Case try executes completely and catch is ignored. Case With Exception If:ArithmeticExceptionoccurs: the try block is interrupted; the matching catch block executes. Complete Example System.out.print("1, "); try { String s = null; s.length(); } catch (NullPointerException e) { System.out.print("2, "); } System.out.println("3");Output: 1, 2, 3 Exceptions Across Methods Exceptions can travel through multiple methods. Example:void f() { try { g(); } catch (ArithmeticException e) { ... } }If:g()throws an exception: it propagates upward to f(). Long-Distance Throw One of the greatest advantages of exceptions. An exception can: travel across many method calls; without intermediate methods needing to handle it. Visualization main() | -> f() | -> g() | -> z()If:z()throws an exception: z() stops; then g() stops; then f() receives the exception. Multiple catch Blocks We can handle different errors separately.try { ... } catch (ArithmeticException e) { ... } catch (ArrayIndexOutOfBoundsException e) { ... } Catch Order Java uses the first compatible catch. Important Example catch (RuntimeException e)captures: ArithmeticException; NullPointerException; etc. Because they all derive from:RuntimeException