JAVA Programming Questions and Answers Latest Update Graded A+

JAVA Programming Questions and Answers Latest Update Graded A+ What is the purpose of the `final` keyword in Java? The `final` keyword is used to declare constants, prevent method overriding, and restrict inheritance. Can a Java class inherit multiple classes? No, Java does not support multiple inheritance with classes to avoid ambiguity, but it allows multiple interface implementations. How do you create an infinite loop in Java? By using `while(true) { }` or `for(;;) { }`, the loop runs indefinitely unless broken with `break` or `return`. What happens if the `main` method is declared as private? The program will compile but will not execute, resulting in a runtime error. Can a constructor be marked as `static` in Java? 2 No, constructors cannot be `static` because they belong to the instance, not the class. How does Java achieve platform independence? Java compiles code into bytecode, which runs on the Java Virtual Machine (JVM) instead of directly on an operating system. What is the difference between `==` and `.equals()` in Java? `==` compares memory references, while `.equals()` compares object values if properly overridden. Can a Java interface have constructors? No, interfaces cannot have constructors because they cannot be instantiated directly. What is method overloading in Java? Method overloading is defining multiple methods with the same name but different parameters within the same class. What will happen if you call `S(0)` in Java? 3 It will terminate the Java Virtual Machine (JVM) immediately. Can a class be both `final` and `abstract` in Java? No, because `final` prevents inheritance, while `abstract` requires subclassing to provide implementations. How can you make an object immutable in Java? Declare the class as `final`, make all fields `private` and `final`, and provide no setters. Can a `static` method access instance variables? No, `static` methods belong to the class and cannot access instance variables directly. What is a marker interface in Java? A marker interface is an interface with no methods, used to signal behavior to the JVM, such as `Serializable`. How does Java handle memory management? 4 Java manages memory using automatic garbage collection, which removes unreachable objects. What is the purpose of the `transient` keyword in Java? The `transient` keyword prevents a variable from being serialized. What is the difference between `HashMap` and `Hashtable`? `HashMap` is not synchronized and allows `null` keys, while `Hashtable` is synchronized and does not allow `null` keys.