throw and throws in java  

throw and throws in java  

Throwing an exception is the last resort that a method invokes when it cannot return a valid result. Throwing an exception is similar to raising your hand in class and asking the professor for help.

This action alerts the calling method that something went wrong and it needs to take further action to resolve the problem. It is also akin to alerting other students in the class so that they can avoid sitting next to you again.

throw and throws in java

Let’s take a look at how we can throw an exception in Java, what type of exceptions exist, and how you can use them effectively.

Throwing an Exception – throw and throws in java

An exception is an abnormal event or condition that disrupts the normal flow of program execution. The purpose of throwing an exception is to signal that an error or other problem has occurred, and to provide information about the problem so that the program can take appropriate action.

When a method cannot execute successfully, it should throw an exception to signal the error to the calling method. This expectation is also applicable to the calling method, which should catch the exception and take the necessary action.

What is an Exception? – throw

and throws in java

An exception is a condition that disrupts the normal flow of program execution and is not part of the normal control flow of the program.

The purpose of throwing an exception is to signal that an error or other problem has occurred, and to provide information about the problem so that the program can take appropriate action.

Exceptions can be caused by erroneous inputs, erroneous outputs, and program errors, such as attempting to divide by zero. Exceptions can also be caused by external factors, such as a device failing to respond as expected.

Java Exceptions – throw and throws in java

Exceptions are simply pieces of data, represented by objects, that describe a problem that occurred while executing a program.

A program that might result in an error can throw an exception. For example, a program that adds two numbers and then attempts to assign the result to a variable that is not large enough to hold the sum, may attempt to write past the end of the assigned area.

The computer detects this situation as an error and throws an exception (the exception being an out-of-bounds write).

The program that attempted to assign the sum to the variable can catch the exception and take an appropriate action, such as trying the addition again without writing past the end of the variable.

The Java programming language uses exceptions for a variety of situations. For example, if a required method cannot be found, or if an invalid method is attempted, an exception is generated and your program can take appropriate action.

Standard Exception Classes – throw and throws in java  

The Java programming language has a number of built-in exception classes, which can be categorized as follows:

– Runtime Exceptions – These exceptions are generated at run time. The decision to throw one of these exceptions can be made at the time the program is running.

– Error Exceptions – These exceptions are generated when the program attempts to execute but cannot perform as expected. The decision to throw one of these exceptions can be made when the program is written.

User-Defined Exceptions – throw and throws in java 

If none of the exceptions listed above fit the bill, you can create your own custom exception class by extending the java.lang.Exception class.

Every exception class must inherit from the base class java.lang.Exception . While it is not mandatory, you should prefix the name of your custom exception class with “Error” (e.g. ErrorMyException).

When you extend Exception, you have access to all of its public fields and methods. This includes the stack trace, which gives you access to the call stack and local variables. You can use this information to generate a meaningful error message for your users.

When to use Throwing and Raising Exceptions – throw and throws in java  

Once you decide to throw an exception, you need to ask yourself a few questions. The most important one is: why can’t my method return a valid result? There are many valid reasons you may not be able to return a valid result. Let’s consider an example.

You are writing a method which calculates the average marks obtained by students in your department. You need to use the average marks of 10 students.

You can either hardcode the values in your method or you can pass them as parameters. Let’s consider both of these options.

If you hardcode the values in your method, you have a number of scenarios where you will not be able to calculate the average properly.

For example, if the marks of one of the students is “0”, your method will throw an exception because you are trying to average the marks of 10 students, but one of the students has a “0” mark.

If you decide to pass the values as parameters, you can always change the values while debugging if one of the students in your department has a 0 mark.

But your method will not throw an exception when you are done debugging. You can simply change the values, recompile your code, and distribute it to your colleagues.

Summarythrow and throws in java  

Exception handling is an important part of every programming language. The main purpose of throwing an exception is to signal that an error or other problem has occurred, and to provide information about the problem so that the program can take appropriate action.

Exceptions can be caused by erroneous inputs, erroneous outputs, and program errors, such as attempting to divide by zero. Exceptions can also be caused by external factors, such as a device failing to respond as expected.

The Java programming language uses exceptions for a variety of situations. The most important thing while deciding to throw an exception is to ask yourself a few questions. Once you have the answers, you know when and when not to throw an exception.

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