Handling Java Exceptions - datacouch-io/spark-java GitHub Wiki

During the execution of Java code, various types of errors can occur. These errors may result from mistakes made by the programmer, incorrect input, or unforeseen issues. When an error occurs, Java typically halts and generates an error message. In technical terms, Java throws an exception to indicate the error.

Using Java's Try and Catch

Java provides a mechanism to handle exceptions using the try and catch blocks. These constructs allow you to gracefully manage errors and continue the program's execution, even when issues arise.

The try Block

The try statement is used to define a block of code that is susceptible to errors while it's being executed. Code within this block is monitored for potential exceptions.

The catch Block

The catch statement is used to define a block of code that will be executed if an error, specified by its type, occurs within the associated try block.

These try and catch blocks are always used in pairs, like so:

try {
  // Code block to try
} catch (ExceptionType e) {
  // Code block to handle errors
}

Here's an example of how to use try and catch to manage an error:

public class MyClass {
  public static void main(String[] args) {
    try {
      int[] myNumbers = {1, 2, 3};
      System.out.println(myNumbers[10]);
    } catch (Exception e) {
      System.out.println("Something went wrong.");
    }
  }
}

In the above code, the try block attempts to access an element at index 10 of an array. However, since the array only has elements at indices 0, 1, and 2, an error occurs. The catch block catches this exception, and the program proceeds with the error-handling code.

The finally Block

The finally statement allows you to execute code after the try and catch blocks, regardless of whether an exception occurred or not. This can be useful for tasks like cleanup or resource management.

Here's an example:

public class MyClass {
  public static void main(String[] args) {
    try {
      int[] myNumbers = {1, 2, 3};
      System.out.println(myNumbers[10]);
    } catch (Exception e) {
      System.out.println("Something went wrong.");
    } finally {
      System.out.println("The 'try catch' block is finished.");
    }
  }
}

In this example, whether or not an exception is caught, the finally block will always execute after the try and catch blocks, allowing you to perform necessary cleanup or logging operations.

By using try, catch, and finally blocks effectively, you can manage exceptions in your Java code and ensure that your programs handle errors gracefully.