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Java throw или throws

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  1. Java throw and throws Keywords
  2. Java throw или throws
  3. throw vs. throws in Java
  4. Comparison Table
  5. throw code
  6. throws code
  7. Java Throw VS Throws: When And How To Use Each
  8. Understanding Java Exceptions
  9. What Are Exceptions In Java?
  10. The Importance Of Handling Exceptions
  11. Types of Exceptions: Checked And Unchecked

Java throw and throws Keywords

In Java exception handling, throw keyword is used to explicitly throw an exception from a method or constructor. And throws keyword is used to declare the list of exceptions that may be thrown by that method or constructor.

Let us learn basic things about throw keyword before going deep.

To throw an exception from a method or constructor, use throw keyword along with an instance of exception class.

1.2. Handling Checked vs Unchecked Exceptions

If we throw an unchecked exception from a method, it is not mandatory to handle the exception or declare in throws clause. For example, NullPointerException is an unchecked exception.

public class JavaExample < public static void main(String[] args) < method(); >public static void method( ) < throw new NullPointerException(); >>

But if we throw a checked exception using throw statement, we MUST either handle the exception in catch block or method must explicitly declare it using throws declaration. For example, FileNotFoundException is a checked exception.

public class JavaExample < public static void main(String[] args) < try < method(); >catch (FileNotFoundException e) < e.printStackTrace(); >> public static void method() throws FileNotFoundException < throw new FileNotFoundException(); >>

In Java, every subclass of Error and RuntimeException is an unchecked exception. A checked exception is everything else under the Throwable class.

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An exception propagates from method to method, up the call stack, until it’s caught. So if a() calls b(), which calls c(), which calls d(), and if d() throws an exception, the exception will propagate from d to c to b to a, unless one of these methods catches the exception.

The search for exception handler begins with the method in which the error occurred and proceeds through the call stack in the reverse order in which the methods were called, as described above.

When an appropriate handler (catch block) is found, the runtime system passes the exception to the handler. If no exception handler is found then exception reaches to JVM’s default exception handler which prints the exception details to logs and terminates the application.

Java throws keyword is used to declare a list of exceptions that may occur during the method execution.

To declare the list of exceptions, use throws keyword along with exception class names.

public static void method( ) throws FileNotFoundException, ConnectionException < //code >

2.2. Allowed to throw checked and unchecked exceptions

We can declare both types of exceptions using throws clause i.e. checked and unchecked exceptions. But the method calling the given method must handle only checked exceptions. Handling unchecked exceptions is optional.

public class JavaExample < public static void main(String[] args) < try < //Can skip handling of NullPointerException (unchecked exception) method(); >catch (FileNotFoundException e) < e.printStackTrace(); >> public static void method() throws NullPointerException, FileNotFoundException < //code >>

3. Difference between throw and throws in Java

  • throw keyword is used to throw a single exception explicitly from any method or constructor while throws keyword is used in method and constructor declaration, denoted which exception can possibly be thrown by this method.
  • throw is followed by an instance of exception class while throws is followed by exception class name.
  • throw is used within the method and constructor where as throws is used with the method and constructor signature.
  • We can throw only single exceptions using throw, but we can declare multiple exceptions using throws one of which may or may not throw by method.
  • A checked exception is propagated to the caller method, while unchecked exceptions are not propagated and thus may not require explicit exception handling.
  • Using throw keyword we can also break a switch statement or a loop without using break keyword which cannot be performed using throws.

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Java throw или throws

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throw vs. throws in Java

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throw and throws are the two keywords used to declare an exception in Java. They are very useful for programmers who have to handle exceptions.

Comparison Table

Throw Throws
throw is followed by an instance. For example: throw new SQLException(“SQL Exception”); throws is followed by a class name i.e., throws SQLException;
throw is used within a method. throws is used next to the method signature.
A programmer cannot throw multiple throws at a single time. A programmer can throw multiple throws at a single time. For example: throws IOException, ArithmeticException;
The throw keyword explicitly throws an exception. The throws keyword declares an exception and works similarly to the try-catch block.

throw code

The following example shows how to use the throw keyword in Java; it displays the exception once it occurs.

class Code 
void checkMarks(int marks) 
if(marks<50)
 
throw new ArithmeticException("Exam failed");
 
else
 
System.out.println("Exam passed");
 
>
 
public static void main(String args[]) 
Code object = new Code();
 
object.checkMarks(43);
 
>
 
>

throws code

The following example explains how to use the throws keyword in java.

class Code 
int checkMarks(int marks) throws ArithmeticException
 
 
int result= marks/0;
 
return result;
 
>
 
public static void main(String args[])
 
 
Code object = new Code();
 
try
 
 
System.out.println (object.checkMarks(43));
 
>
 
catch(ArithmeticException except)
 
 
System.out.println("Error in dividing number by zero");
 
>
 
>
>

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Java Throw VS Throws: When And How To Use Each

Java Throw VS Throws: When And How To Use Each

Unravel the mystery of Java’s throw and throws keywords. This article offers a deep dive into understanding their unique roles, common pitfalls, and best practices. It’s a must-read for budding Java developers!

Ah, Java, the programming language that’s as invigorating as a cup of its namesake beverage. It’s a language that’s robust, versatile, and sometimes, just like your coffee, can be a little bitter if not handled correctly. One such bitter aspect? Exception handling.

In the world of Java, exceptions are like those pesky coffee grounds that somehow sneak past your filter. They’re unexpected, unwanted, and can ruin an otherwise smooth experience.

But fear not, Java developers, for we have the tools to handle these exceptions — the throw and throws keywords.

Throw and throws in Java are like the barista and coffee machine of your local café. They handle the hot, pressurized, and potentially messy process of making your coffee (or in this case, running your code), ensuring that any mishaps are dealt with swiftly and efficiently.

Now, imagine you’re a newbie barista, just starting to learn the ropes. The coffee machine (Java) is a complex beast, and you need to understand how to operate it safely. That’s where this article comes in. We’re going to dive into the nitty-gritty of throw and throws , helping you understand when and how to use each.

So, put on your metaphorical barista apron, and let’s get brewing! And remember, in the world of Java, a good developer is like a good barista — always ready to handle the unexpected.

Important disclosure: we’re proud affiliates of some tools mentioned in this guide. If you click an affiliate link and subsequently make a purchase, we will earn a small commission at no additional cost to you (you pay nothing extra). For more information, read our affiliate disclosure.

Understanding Java Exceptions

In the grand opera of programming, exceptions are the divas. They demand attention, they disrupt the flow, and if not handled properly, they can bring the whole performance to a screeching halt.

But just like divas, exceptions in Java are not inherently bad. They’re simply a signal that something out of the ordinary has occurred, and it’s time for some special handling.

What Are Exceptions In Java?

In Java, an exception is an event that disrupts the normal flow of the program. It’s like a cat running across your keyboard in the middle of a coding marathon. You didn’t expect it, you didn’t want it, but there it is — and now you have to deal with it.

Exceptions can occur for a variety of reasons, from user input errors to resource failures. For example, trying to divide by zero, accessing a null object, or attempting to read a file that doesn’t exist can all trigger exceptions.

The Importance Of Handling Exceptions

Ignoring exceptions in Java is like ignoring that check engine light in your car. Sure, the car might still run for a while, but sooner or later, you’re going to find yourself stranded on the side of the road. Similarly, unhandled exceptions can cause your program to terminate unexpectedly, leading to a poor user experience and potential data loss.

Types of Exceptions: Checked And Unchecked

Java exceptions come in two flavors: checked and unchecked, kind of like your luggage at the airport.

Checked exceptions are like your checked luggage — the compiler checks them at compile-time, and you’re required to declare them in your method or constructor’s throws clause. If you don’t, the compiler will complain, much like an airport security officer would if you tried to bring a full-sized shampoo bottle in your carry-on.

On the other hand, unchecked exceptions are like your carry-on luggage — the compiler doesn’t check them at compile-time. These are usually programming errors, like trying to access an out-of-bounds array or a null object.

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