NullPointerException is a runtime exception in Java that occurs when a variable is accessed which is not pointing to any object and refers to nothing or null. Since the NullPointerException is a runtime exception, it doesn’t need to be caught and handled explicitly in application code.
How do you handle NullPointerException?
Effective Java NullPointerException Handling
- Check Each Object For Null Before Using.
- Check Method Arguments for Null.
- Consider Primitives Rather than Objects.
- Carefully Consider Chained Method Calls.
- Make NullPointerExceptions More Informative.
How do I fix Java Lang NullPointerException?
In Java, the java. lang. NullPointerException is thrown when a reference variable is accessed (or de-referenced) and is not pointing to any object. This error can be resolved by using a try-catch block or an if-else condition to check if a reference variable is null before dereferencing it.
What is Java Lang NullPointerException error?
The java. lang. NullPointerException is an error in Java that occurs as a Java program attempts to use a null when an object is required. Similarly, if an object is null and you try to access or modify the field of that null object, this error will occur.
In which case the NullPointerException will be thrown?
A null pointer exception is thrown when an application attempts to use null in a case where an object is required. These include: Calling the instance method of a null object. Accessing or modifying the field of a null object.
What is FileNotFoundException in Java?
java.io.FileNotFoundException. Signals that an attempt to open the file denoted by a specified pathname has failed. This exception will be thrown by the FileInputStream, FileOutputStream, and RandomAccessFile constructors when a file with the specified pathname does not exist.
How do you handle exceptions in Java?
The try-catch is the simplest method of handling exceptions. Put the code you want to run in the try block, and any Java exceptions that the code throws are caught by one or more catch blocks. This method will catch any type of Java exceptions that get thrown. This is the simplest mechanism for handling exceptions.
What is Java lang?
Provides classes that are fundamental to the design of the Java programming language. The most important classes are Object, which is the root of the class hierarchy, and Class, instances of which represent classes at run time.
What is a number format exception?
The NumberFormatException occurs when an attempt is made to convert a string with improper format into a numeric value. That means, when it is not possible to convert a string in any numeric type (float, int, etc), this exception is thrown.
What is a class cast exception?
Class ClassCastException Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance.
How do I fix NullPointerException in Android?
Handling the NullPointerException in Android Studio
- Try: The Try block executes a piece of code that is likely to crash or a place where the exception occurs.
- Catch: The Catch block will handle the exception that occurred in the Try block smoothly(showing a toast msg on screen) without letting the app crash abruptly.
How do I fix ClassNotFoundException?
How to Resolve ClassNotFoundException in Java
- Find out which JAR file contains the problematic Java class.
- Check whether this JAR is present in the application classpath.
- If that JAR is already present in the classpath, make sure the classpath is not overridden (e.g. by a start-up script).
What is the null in Java?
In Java, null is a reserved word for literal values. It seems like a keyword, but actually, it is a literal similar to true and false.
Is FileNotFoundException a runtime exception?
FileNotFoundException occurs at runtime so it is a checked exception, we can handle this exception by java code, and we have to take care of the code so that this exception doesn’t occur.
How do I stop null dereference in Java?
Answer: Some of the best practices to avoid NullPointerException are:
- Use equals() and equalsIgnoreCase() method with String literal instead of using it on the unknown object that can be null.
- Use valueOf() instead of toString(); and both return the same result.
- Use Java annotation @NotNull and @Nullable.
What is Arrayindexoutofbound exception in Java?
If a request for a negative or an index greater than or equal to the size of the array is made, then the JAVA throws an ArrayIndexOutOfBounds Exception. The ArrayIndexOutOfBoundsException is a Runtime Exception thrown only at runtime. The Java Compiler does not check for this error during the compilation of a program.