Java throw exception with object

Java throw exception with object

• Introduction to Java
• The complete History of Java Programming Language
• C++ vs Java vs Python
• How to Download and Install Java for 64 bit machine?
• Setting up the environment in Java
• How to Download and Install Eclipse on Windows?
• JDK in Java
• How JVM Works – JVM Architecture?
• Differences between JDK, JRE and JVM
• Just In Time Compiler
• Difference between JIT and JVM in Java
• Difference between Byte Code and Machine Code
• How is Java platform independent?

• Decision Making in Java (if, if-else, switch, break, continue, jump)
• Java if statement with Examples
• Java if-else
• Java if-else-if ladder with Examples
• Loops in Java
• For Loop in Java
• Java while loop with Examples
• Java do-while loop with Examples
• For-each loop in Java
• Continue Statement in Java
• Break statement in Java
• Usage of Break keyword in Java
• return keyword in Java

• Object Oriented Programming (OOPs) Concept in Java
• Why Java is not a purely Object-Oriented Language?
• Classes and Objects in Java
• Naming Conventions in Java
• Java Methods
• Access Modifiers in Java
• Java Constructors
• Four Main Object Oriented Programming Concepts of Java
• Inheritance in Java
• Abstraction in Java
• Encapsulation in Java
• Polymorphism in Java
• Interfaces in Java
• ‘this’ reference in Java

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How to Throw Exceptions

Before you can catch an exception, some code somewhere must throw one. Any code can throw an exception: your code, code from a package written by someone else such as the packages that come with the Java platform, or the Java runtime environment. Regardless of what throws the exception, it’s always thrown with the throw statement.

As you have probably noticed, the Java platform provides numerous exception classes. All the classes are descendants of the Throwable class, and all allow programs to differentiate among the various types of exceptions that can occur during the execution of a program.

You can also create your own exception classes to represent problems that can occur within the classes you write. In fact, if you are a package developer, you might have to create your own set of exception classes to allow users to differentiate an error that can occur in your package from errors that occur in the Java platform or other packages.

You can also create chained exceptions. For more information, see the Chained Exceptions section.

The throw Statement

All methods use the throw statement to throw an exception. The throw statement requires a single argument: a throwable object. Throwable objects are instances of any subclass of the Throwable class. Here’s an example of a throw statement.

throw someThrowableObject;

Let’s look at the throw statement in context. The following pop method is taken from a class that implements a common stack object. The method removes the top element from the stack and returns the object.

public Object pop() < Object obj; if (size == 0) < throw new EmptyStackException(); > obj = objectAt(size - 1); setObjectAt(size - 1, null); size--; return obj; >

The pop method checks to see whether any elements are on the stack. If the stack is empty (its size is equal to 0 ), pop instantiates a new EmptyStackException object (a member of java.util ) and throws it. The Creating Exception Classes section in this chapter explains how to create your own exception classes. For now, all you need to remember is that you can throw only objects that inherit from the java.lang.Throwable class.

Note that the declaration of the pop method does not contain a throws clause. EmptyStackException is not a checked exception, so pop is not required to state that it might occur.

Throwable Class and Its Subclasses

The objects that inherit from the Throwable class include direct descendants (objects that inherit directly from the Throwable class) and indirect descendants (objects that inherit from children or grandchildren of the Throwable class). The figure below illustrates the class hierarchy of the Throwable class and its most significant subclasses. As you can see, Throwable has two direct descendants: Error and Exception .

Error Class

When a dynamic linking failure or other hard failure in the Java virtual machine occurs, the virtual machine throws an Error . Simple programs typically do not catch or throw Error s.

Exception Class

Most programs throw and catch objects that derive from the Exception class. An Exception indicates that a problem occurred, but it is not a serious system problem. Most programs you write will throw and catch Exception s as opposed to Error s.

The Java platform defines the many descendants of the Exception class. These descendants indicate various types of exceptions that can occur. For example, IllegalAccessException signals that a particular method could not be found, and NegativeArraySizeException indicates that a program attempted to create an array with a negative size.

One Exception subclass, RuntimeException , is reserved for exceptions that indicate incorrect use of an API. An example of a runtime exception is NullPointerException , which occurs when a method tries to access a member of an object through a null reference. The section Unchecked Exceptions — The Controversy discusses why most applications shouldn’t throw runtime exceptions or subclass RuntimeException .

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Java throw exception with object

правильно ли понимаю, что когда я работаю с проектом, в котором есть несколько потоков исполнения, может быть вот такая ситуация. Один из этих потоков запускается и завершается успешно, а затем выбрасывает исключение внутри блока try-catch. Оставшиеся потоки исполнения продолжают свою работу, но никакой код в блоке finally не выполняется. Тогда блок finally при обработке исключений не будет выполнен?

я читаю про исключения на 1м и в принципе понимаю, но не очень. ps: зачем только я начал с java core. pss: если вы это читаете, и я до сих пор на первом, то либо я прохожу другой курс, либо читаю книгу по джаве, параллельно проходя этот курс, либо решил взять перерыв на неопределенный срок времени. никогда не сдамся)

Есть подозрение, что так будет правильнее.

обращу внимание на некоторую неточность. цитата «Создание исключения При исполнении программы исключение генерируется JVM или вручную, с помощью оператора throw» в java исключения это тоже объекты поэтому создается исключение так же как объект new Exception. а бросается в программе с помощью оператора throw. обычно эти операции объединяют в одну throw new Exception(«aaa»);

если что я пишу это с 3 уровня. Под конец лекций я читал статью про бафридер, после нашел там ссылку на потоки вводов, а потом чтобы понять что там говориться ввел гугл про исключение и нашел эту статью, спасибо автору, это статья очень помогла. PS если ты читаешь этот комментарий и видишь что у меня нет прогресса(то есть если я все еще на 3 уровне или чуточку больше), то скажи мне, что я нуб и не дошел до 40 лвла

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