Difference between NoClassDefFoundError vs ClassNotFoundExcepiton in Java

Both NoClassDefFoundError and ClassNotFoundException are dangerous errors that come when JVM or ClassLoader not able to locate class during the class loading process. Since different ClassLoader loads classes from a different location, sometimes this issue may be caused because of incorrect CLASSPATH as well i.e. some JAR files from lib are missing or from the old version. Though looks quite similar there is a subtle difference between NoClassDefFoundError and ClassNotFoundException, NoClassDefFoundError indicates that the class was present during the time of compilation but not available when you run Java program, sometimes error on static initializer block can also result in NoClassDefFoundError.

Difference between Public, Package, Private and Protected in Java?

In Java, you have got something called an access modifier, which specifies the accessibility of class, methods, and variables. There is four access modifier in Java namely public, private, protected and the default access modifier, also known as package level modifier. The difference between these access modifiers comes in their ability to restrict access to a class, method, or variables, public is the least restrictive access modifier while private is the most restrictive access modifier, package, and protected lies in between.

Difference between HashSet vs TreeSet in Java? [Answer]

HashSet and TreeSet both implement same interface i.e java.util.Set interface and they possess the quality of Set interface means duplicate elements are not allowed. Both HashSet and TreeSet are used to store unique elements, but HashSet doesn't care about any order and TreeSet keeps a thing in order. Ordering or sorting on TreeSet can be customized by using the Comparator interface, by default TreeSet uses elements of natural order for sorting, which is defined by the compareTo() method of java.lang.Comparable interface. What is the difference between HashSet and TreeSet is also one of the frequently asked Java interview questions, So you should know about similarities and differences between them?

What is fail safe and fail fast Iterator in Java?

Java Collections supports two types of Iterator, fail-safe and fail fast. The main distinction between a fail-fast and fail-safe Iterator is whether or not the underlying collection can be modified while it begins iterated. If you have used Collection like ArrayList then you know that when you iterate over them, no other thread should modify the collection. If the Iterator detects any structural change after iteration has begun e.g adding or removing a new element then it throws ConcurrentModificationException, this is known as fail-fast behavior and these iterators are called fail-fast iterator because they fail as soon as they detect any modification.

Difference between ROW_NUMBER(), RANK() and DENSE_RANK() in SQL

The main difference between ROW_NUMBER() and RANK() in SQL server is that ROW_NUMBER doesn't handle ties while RANK() does. Though both ROW_NUMBER() and RANK() are window function used for ranking row, the way they handle duplicates differentiate them. ROW_NUMBER() function assigns a unique number to each row starting from 1 and arbitrarily assign values if two rows are equal, which means it's not guaranteed that which row will get 2nd or 3rd position if they are identical. In contrast, RANK() assigns an equivalent rank to similar rows, which creates gaps between RANK.

Difference between Method and Constructor in Java and OOP? Example

What is the difference between method and constructor in Java is a very common question in beginner-level Java interviews with 2 to 3-year experience. Since the constructor is kind of special and it has its own properties that separate it from any normal Java method, this question makes sense. The main difference between a Constructor and a Method is that you need to call the method explicitly but the constructor is called implicitly by the Java programming language during object instantiation. This is one of the special properties of constructors in Java and that's why all the object initialization code is put inside the constructor.

What is static in Java? Example Tutorial

What is static in Java
Static in Java is related to class if a field is static means it belongs to the class, similarly static method belongs to classes and you can access both static method and field using the class name, for example, if count field is static in Counter class than you can access it as Counter.count, of course, subject to restriction applied by access modifier like private fields are only accessible in class on which they are declared, protected fields are accessible to all classes in the same package but only accessible in subclass outside the package, you can further see private vs protected vs public for complete details on access modifier.

Can you make an Abstract Class or Method Final in Java? Example

No, you cannot make an abstract class or method final in Java because the abstract and final are mutually exclusive concepts. An abstract class is incomplete and can only be instantiated by extending a concrete class and implementing all abstract methods, while a final class is considered complete and cannot be extended further. This means when you make an abstract class final, it cannot be extended hence it cannot be used and that's why the Java compiler throws a compile-time error when you try to make an abstract class final in Java. In short, an abstract class cannot be final in Java, using both abstract and final modifiers with a class is illegal in Java.

Java67

Pages

Top 5 Java Main method Interview Questions with Answers