what are the difference between abstract class and interface, and throw and throws, and why we use throws?? Why String is Immutable?

Question

Accepted Answer

Explaining differences between abstract class and interface, throw and throws, and why we use throws. Also, why String is immutable.

Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
A class can implement multiple interfaces, but can only extend one abstract class.
Throw is used to explicitly throw an exception, while throws is used to declare the exceptions that a method may throw.
We use throws to inform the caller of a method that it may throw an exception, so that the caller can handle it appropriately.
String is immutable because it enhances security, improves performance, and simplifies coding.
Immutable objects are thread-safe and can be shared without synchronization.
String pool is possible because of immutability, which saves memory and improves performance.

Accepted Answer

Abstract classes can have methods with implementation whereas interface provides absolute abstraction and can't have any method implementations.

Accepted Answer

Definition: An abstract class is a class that cannot be instantiated and can contain both abstract and non-abstract methods. An interface, on the other hand, is a contract that specifies a set of methods that a class must implement.

Accepted Answer

throw and throws keyword related to exception handling which are used to
throw-> throw exception inside a method manually
throws-> use with method or class signature to handle exception

Accepted Answer

Abstract and interface are used to get the abstraction in java Basically data hiding Abstract class can have Abstract and non abstract method Interface will have all variables as final and Abstract and from java 8 one default method String is immutable because memory in string pool cannot be changed eve the string variable is created

Accepted Answer

interface is 100% incomplete
interface supports multiple inheritance
all variable by default are final and static
interface can't consist of constructor

abstract can be 0 to 100% incomplete
abstract can't support multiple inheritance
all variable can be static, non-static and final
abstract class can consist of constructor

throws keyword apply on a method
if any exception happens on a method then that exception will passed to the method calling statement

throw keyword helps to create customized exception as per the developer requirement

because String value can't be changed

to handle exception

what are the difference between abstract class and interface, and throw and throws, and why we use throws?? Why String is Immutable?

Top TCS Java Developer interview questions & answers

Popular interview questions of Java Developer

Top HR questions asked in TCS Java Developer