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Core java - Interview Questions and Answers for 'Barclays' - 5 question(s) found - Order By Newest | ||||
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Ans. 1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references. Example - String str1 = "String1"; String str2 = "String1"; // It doesn't create a new String and rather reuses the string literal from pool // Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too 2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence it's not fit to be cached. 3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment. | ||||
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Ans. Checked exceptions are the exceptions for which compiler throws an errors if they are not checked whereas unchecked exceptions are caught during run time only and hence can't be checked. | ||||
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Ans. Its a facility for code reuse and independent extension wherein a derived class inherits the properties of parent class. | ||||
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Ans. B ctor B ctor B ctor A ctor A ctor | ||||
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Ans. Assigning a value of one type to a variable of another type is known as Type Casting. Example : int x = 10; byte y = (byte)x; In Java, type casting is classified into two types, Widening Casting(Implicit) widening-type-conversion and Narrowing Casting (Explicitly done) narrowing-type-conversion. Widening or Automatic type converion - Automatic Type casting take place when,the two types are compatible and the target type is larger than the source type Example : public class Test { public static void main(String[] args) { int i = 100; long l = i; //no explicit type casting required float f = l;//no explicit type casting required System.out.println("Int value " i); System.out.println("Long value " l); System.out.println("Float value " f); } } Narrowing or Explicit type conversion - When you are assigning a larger type value to a variable of smaller type, then you need to perform explicit type casting. Example : public class Test{ public static void main(String[] args) { double d = 100.04; long l = (long)d; //explicit type casting required int i = (int)l;//explicit type casting required System.out.println("Double value " d); System.out.println("Long value " l); System.out.println("Int value " i); } } | ||||
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