What is Java Lang ClassCastException in Java?

What is a Java Lang ClassCastException?

java.lang.ClassCastException. Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance. For example, the following code generates a ClassCastException : Object x = new Integer(0); System.out.println((String)x);

How do I resolve Java Lang ClassCastException error?

Ensure that the new type belongs to one of its parent classes. You can prevent the ClassCastException by using Generics, because Generics provide compile time checks and can be used to develop type-safe applications.

What causes a ClassCastException?

When will be ClassCastException is thrown

When we try to cast an object of Parent class to its Child class type, this exception will be thrown. When we try to cast an object of one class into another class type that has not extended the other class or they don’t have any relationship between them.

Can we catch ClassCastException?

What you can do is pass in an instance of the Class of the parameterised type (assuming it isn’t generic). class MyReader<T> { private final Class<T> clazz; MyReader(Class<T> clazz) { if (clazz == null) { throw new NullPointerException(); } this. clazz = clazz; } public T restore(String from) { …

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How do you handle Java Lang ExceptionInInitializerError?

We can resolve the java. lang. ExceptionInInitializerError by ensuring that static initializer block of classes does not throw any Runtime Exception. We can resolve also resolve this exception by ensuring that the initializing static variable of classes also doesn’t throw any Runtime Exception.

Why do we get ClassCastException in Java?

ClassCastException is a runtime exception raised in Java when we try to improperly cast a class from one type to another. It’s thrown to indicate that the code has attempted to cast an object to a related class, but of which it is not an instance.

How do you resolve ClassCastException?

In order to deal with ClassCastException be careful that when you’re trying to typecast an object of a class into another class ensure that the new type belongs to one of its parent classes or do not try to typecast a parent object to its child type.

Is NullPointerException checked or unchecked?

Answer: NullPointerException is not a checked exception. It is a descendant of RuntimeException and is unchecked.

How Downcasting is possible in Java?

When Subclass type refers to the object of Parent class, it is known as downcasting. If we perform it directly, compiler gives Compilation error. … But if we use instanceof operator, downcasting is possible.

How does try finally work java?

finally defines a block of code we use along with the try keyword. It defines code that’s always run after the try and any catch block, before the method is completed. The finally block executes regardless of whether an exception is thrown or caught.

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How do you handle Java Lang IllegalArgumentException?

When an IllegalArgumentException is thrown, we must check the call stack in Java’s stack trace and locate the method that produced the wrong argument. The IllegalArgumentException is very useful and can be used to avoid situations where the application’s code would have to deal with unchecked input data.

What does Java Lang IndexOutOfBoundsException mean?

IndexOutOfBoundsException is a subclass of RuntimeException mean it is an unchecked exception which is thrown to indicate that an index of some sort (such as to an array, to a string, or to a vector) is out of range. e.g using List.

What is throw and throws in Java?

Both throw and throws are concepts of exception handling in Java. The throws keyword is used to declare which exceptions can be thrown from a method, while the throw keyword is used to explicitly throw an exception within a method or block of code.

What causes null pointer exception in Java?

What Causes NullPointerException. The NullPointerException occurs due to a situation in application code where an uninitialized object is attempted to be accessed or modified. Essentially, this means the object reference does not point anywhere and has a null value.

Can we cast parent to child in Java?

However, we can forcefully cast a parent to a child which is known as downcasting. After we define this type of casting explicitly, the compiler checks in the background if this type of casting is possible or not. If it’s not possible, the compiler throws a ClassCastException.