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| Core java - Interview Questions and Answers for 'Vitech systems' - 2 question(s) found - Order By Newest | ||||
 Very Frequently asked. Have been asked in HCL Technologies very frequently ( based on 3 feedback ). Among first few questions in many interviews. | ||||
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| Ans. Abstract classes can have both abstract methods ( method declarations ) as well as concrete methods ( inherited to the derived classes ) whereas Interfaces can only have abstract methods ( method declarations ). A class can extend single abstract class whereas it can implement multiple interfaces. | ||||
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 Discuss Correct / Improve  java classes abstract class interfaces abstract class vs interface abstract classes vs interfaces  Asked in 82 Companies  basic  frequent | ||||
 Related Questions | ||||
 What are the different uses of Interfaces in Java ? | ||||
| Why can't we have diamond problem with interfaces ? | ||||
| Why do we need Thread class even in case we execute thread using runnable interface ? | ||||
| What is the difference between List, Set and Map ? or What are the different Java Collections Interfaces ? | ||||
| What are Marker Interfaces ? Name few Java marker interfaces ? | ||||
| Can we declare interface methods as private ? | ||||
| What is comparator interface used for ? | ||||
| What is the use of runnable interface if we can always create a new thread using Thread class ? | ||||
| Which of the following doesn't extend Collection interface ? | ||||
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| Ans. class Student { /// /// /// private int id; private String name; /// /// /// public Student(int id, String name) { this.name = name; this.id = id; }// Student /// /// /// public int getId() { return id; }// getId /// /// /// public void setId(int id) { this.id = id; }// setId /// /// /// public String getName() { return name; }// getName /// /// /// public void setName(String name) { this.name = name; }// setName @Override public boolean equals(Object obj) { if (obj == null) return false; if (!(obj instanceof Student)) return false; if (obj == this) return true; return this.getId() == ((Student) obj).getId(); }// equals /// /// /// @Override public int hashCode() { return this.getId(); }// hashCode }// Student | ||||
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| Related Questions | ||||
| Which String class does not override the equals() and hashCode() methods, inheriting them directly from class Object? | ||||
| How many threads can access a concurrent hashmap when the hashcode is overridden and always returns a zero. | ||||
