SEARCH on "Exceptions" in Java Trial Map
82% The catch Block(s)
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. You associate exception handlers with a try statement by providing one or more catch blocks directly after the try block: try { . . . } catch ( . . . ) { . . . } catch ( . . . ) { . . . } . . . There can be no intervening code between the end of the try statement and the beginning of the first catch statement. The general form of...
82% Catching and Throwing Exceptions
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. Instead, the Java Virtual Machine propagates the error conditions automatically to a location (the catch clause in Java) that can handle the same class of error conditions in a centralized way.callback, as follows: ... jclass cls = (*env)->GetObjectClass(env, obj); jmethodID mid = (*env)->GetMethodID(env, cls, "callback", "()V");...
82% What's an Exception and Why Do I Care?
Summary: If your read_file function used exceptions instead of traditional error management techniques, it would look something like this: readFile { try { open the file; determine its size; allocate that much memory; read the file into memory; close the file; } catch (fileOpenFailed) { doSomething; } catch (sizeDeterminationFailed) { doSomething; } catch (memoryAllocationFailed) { doSomething; } catch...
78% Putting It All Together
Summary: txt") statement can fail for any number of reasons: the user doesn't have write permission on the file or directory, the file system is full, or the directory for the file doesn't exist. However, the FileWriter constructor doesn't have an appropriate exception handler so the runtime system checks the next method in the method call stack--the writeList method. The exception thrown by the FileWriter...
76% Creating Complete JDBC Applications
Summary: First, it prints out all three parts of an SQLException object: the message (a string that describes the error), the SQL state (a string identifying the error according to the X/Open SQLState conventions), and the vendor error code (a number that is the driver vendor's error code number). Severity 16, State 1, Line 1 SQLState: 42501 ErrorCode: 2714 SQLState is a code defined in X/Open and ANSI-92...
74% Changes to the Java Language
Summary: class ClassWithStaticInitializer { static { // ... initialization code ... } } JDK 1.1 adds a similar syntax for performing instance initialization: class ClassWithInstanceInitializer { { // ... initialization code ... } } Initialization code introduced without the static keyword is executed by every constructor, just after the superclass constructor is called, in the same order that they appear...
74% Java's Catch or Specify Requirement
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. The next page, Dealing with Exceptions, introduces an example program, talks about catching exceptions, and shows you how to write an exception handler for the example program. Because any exception that can be thrown by a method is really part of the method's public programming interface: callers of a method must know about the...
72% Dealing with Exceptions
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. Catching and Handling Exceptions will show you how to write exception handlers for both exceptions, and Specifying the Exceptions Thrown by a Method will show you how to specify those exceptions instead of catching them. This section covers the three components of an exception handler--the try, catch, and finally blocks--by...
72% Handling Errors with Exceptions
Summary: Your first encounter with Java exceptions was probably in the form of an error message from the compiler like this one: InputFile. The Java language requires that a method either catch all "checked" exceptions (those that are checked by the runtime system) or specify that it can throw that type of exception. Although Java requires that methods catch or specify checked exceptions, they do not...
70% How to Throw Exceptions
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. Any Java code can throw an exception: your code, code from a package written by someone else (such as the packages that come with the Java development environment), or the Java runtime system. All of these classes are descendants of the Throwable class and allow programs to differentiate between the various types of exceptions...
70% Creating an Applet from an Application
Summary: All applets extend the Applet class; that is, they are subclasses of Applet . Therefore, every applet definition must contain the words extends Applet , as shown here: public class MyAppletName extends Applet { . . . } In our applet example, OutputApplet, this line also includes the words implements Runnable , so it looks like this: public class OutputApplet extends Applet implements Runnable { ....
70% Implementing a Remote Interface
Summary: *; public class ComputeEngine extends UnicastRemoteObject implements Compute { public ComputeEngine() throws RemoteException { super(); } public Object executeTask(Task t) { return t.execute(); } public static void main(String[] args) { if (System. The code for the constructor is public ComputeEngine() throws RemoteException { super(); } This constructor simply calls the superclass constructor,...
70% Control Flow Statements
Summary: By Convention: The opening curly bracket { is at the end of the same line as the while statement, and the closing curly bracket } begins a new line aligned with the while, as shown. You could use an if statement with a series of companion else if statements, and an else to write this code: int testscore; char grade; if (testscore >= 90) { grade = 'A'; } else if (testscore >= 80) {...
70% Creating Your Own Exception Classes
Summary: Also, some legitimate calls to your linked list's methods may result in an undefined result. Each of the methods supported by your linked list might throw an exception under certain conditions, and each method might throw a different type of exception than the others.. Your linked list class can throw multiple exceptions, and it would be convenient to be able to catch all exceptions thrown by...
70% Runtime Exceptions--The Controversy
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. Because the Java language does not require methods to catch or specify runtime exceptions, it's tempting for programmers to write code that throws only runtime exceptions or to make all of their exception subclasses inherit from RuntimeException. Both of these programming shortcuts allow programmers to write Java code without...
70% Catching and Handling Exceptions
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. Now that you've familiarized yourself with the ListOfNumbers class and where the exceptions can be thrown within it, you can learn how to write exception handlers to catch and handle those exceptions. They show you how to write an exception handler for the ListOfNumbers class's writeList method, described in The ListOfNumbers...
70% The Throwable Class and Its Subclasses
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. This includes direct descendants (that is, objects that derive directly from the Throwable class) as well as indirect descendants (objects that derive from children or grandchildren of the Throwable class). When a dynamic linking failure or some other "hard" failure in the virtual machine occurs, the virtual machine throws an...
70% Specifying the Exceptions Thrown by a Method
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. The previous section showed you how to write an exception handler for the writeList method in the ListOfNumbers class. For example, if you were providing the ListOfNumbers class as part of a package of classes, you probably couldn't anticipate the needs of all of the users of your package. To remind you, here's the original...
68% CatchThrow.c
Summary: #include #include "CatchThrow.h" JNIEXPORT void JNICALL Java_CatchThrow_catchThrow(JNIEnv *env, jobject obj) { jclass cls = (*env)->GetObjectClass(env, obj); jmethodID mid = (*env)->GetMethodID(env, cls, "callback", "()V"); jthrowable exc; if (mid == 0) { return; } (*env)->CallVoidMethod(env, obj, mid); exc = (*env)->ExceptionOccurred(env); if (exc) { /* We don't do much with the exception, except...
68% The try Block
Summary: Start of Tutorial > Start of Trail > Start of Lesson Search. In general, a try block looks like this: try { Java statements } The segment of code labelled Java statements is composed of one or more legal Java statements that could throw an exception. To construct an exception handler for the writeList method from the ListOfNumbers class, you need to enclose the exception-throwing...