Java interview questions
- How to retrieve a key and Value from a map ? view answer
- Why can an interface supertype call methods that belong to Object class? view answer
- Q. What is difference between shallow copy and deep copy ? view answer
- Q.Why to override equals() and hashCode()? and How i can implement both equals() and hashCode() for Set ? view answer
- Q.How to sort list of objects ( User Defined) using comparator? in Descending Order. view answer
- Q. How to sort list of objects ( User Defined) using comparator?
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- What is the difference between int and Interger? view answer
- Singleton Double-checked locking in Java?
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- What are the parameters to follow Creating and Destroying Objects in Java? view answer
- Q.What are the different scopes for Java variables?
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- Q.What method must be implemented by all threads?
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- Q.Can an unreachable object become reachable again?
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- Q.What are the steps in the JDBC connection?
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- Q.How are this() and super() used with constructors?
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- Q.What is the difference between static and non-static variables?
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- Q.What is the purpose of finalization?
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- Q.Does garbage collection guarantee that a program will not run out of memory?
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- Q.What is synchronization and why is it important?
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- Q.What is daemon thread and which method is used to create the daemon thread?
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- Q.What are synchronized methods and synchronized statements?
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- Q.If I write System.exit (0); at the end of the try block, will the finally block still execute?
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- Q.If I write return at the end of the try block, will the finally block still execute?
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- Q.Is it necessary that each try block must be followed by a catch block?
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- Q.What is the basic difference between the 2 approaches to exception handling.
1> try catch block and
2> specifying the candidate exceptions in the throws clause?
When should you use which approach?
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- Q.What are the different ways to handle exceptions?
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- Q.What is the difference between error and an exception?
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- Q: What is wrapper class? Explain with example? view answer
- Q.What is serialization? Explain with example? view answer
- Q.What one should take care of while serializing the object?
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- Q. When you serialize an object, what happens to the object references included in the object?
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- Q.What happens to the static fields of a class during serialization?
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- Q. Objects are passed by value or by reference?
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- Q. Primitive data types are passed by reference or pass by value?
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- Q. What type of parameter passing does Java support?
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- Q.Can a top level class be private or protected?
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- Q.What is the default value of an object reference declared as an instance variable?
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- Q.What is the difference between declaring a variable and defining a variable?
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- Q. What are different types of inner classes?
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- Q. What is Overriding? view answer
- Q.What are Checked and UnChecked Exception?
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- Q. What is final?
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- Q.What is static in java? view answer
- What is an abstract class?
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- Q. What are the modifiers in Java ? view answer
- Q.Difference between HashMap and HashTable? view answer
- Q.Difference between Vector and ArrayList? view answer
- Q.Difference between ArrayList and LinkedList? view answer
- Q.What are pass by reference and passby value in Java? view answer
- Q. When we go for Abstract and Interface in Java? view answer
- Q.What is the difference between interface and abstract class? view answer
- Q.What are the Garbage collection algorithms in Java? view answer
- Q.What is garbage collection and the purpose of garbage collection in Java? view answer
- Q. What is the difference between an Interface and an Abstract class?
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!!! Java interview questions !!!
How to retrieve a key and Value from a map ?
Map<String, Object> map = new HashMap<String, Object>();
for (String key : map.keySet()) {
Object value = map.get(key);
// ...
}
OR
class Test{
public static void main(String[] args) {
Map map = new HashMap();
map.put("man", "john");
map.put("woman", "jane");
System.out.println("Key for john is: " +
getKey(map, "john"));
}
private static String getKey(Map map, String value) {
for (Iterator i = map.keySet().iterator(); i.hasNext() {
String key = (String)i.next();
if (map.get(key).equals(value)) {
return key;
}
}
return "No value found";
}
}
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