What is the
difference between an Interface and an Abstract class?
An
abstract class can have instance methods that implement a default behavior. An
Interface can only declare constants and instance methods, but cannot implement
default behavior and all methods are implicitly abstract. An interface has all
public members and no implementation. An abstract class is a class which may
have the usual flavors of class members (private, protected, etc.), but has
some abstract methods.
What is the purpose
of garbage collection in Java, and when is it used?
The
purpose of garbage collection is to identify and discard objects that are no
longer needed by a program so that their resources can be reclaimed and reused.
A Java object is subject to garbage collection when it becomes unreachable to
the program in which it is used.
Describe
synchronization in respect to multithreading.
With
respect to multithreading, synchronization is the capability to control the
access of multiple threads to shared resources. Without synchronization, it is
possible for one thread to modify a shared variable while another thread is in
the process of using or updating same shared variable. This usually leads to
significant errors.
Explain different way
of using thread?
The
thread could be implemented by using runable interface or by inheriting from
the Thread class. The former is more advantageous, because when you are going
for multiple inheritance, the only interface can help.
What are pass by
reference and pass by value?
Pass
By Reference means the passing the address itself rather than passing the
value. Pass by Value means passing a copy of the value to be passed.
What is HashMap and
Map?
Map
is Interface and Hashmap is class that implements that.
Difference between
HashMap and HashTable?
The
HashMap class is roughly equivalent to Hashtable, except that it is
unsynchronized and permits nulls. (HashMap allows null values as key and value
whereas Hashtable does not allow). HashMap does not guarantee that the order of
the map will remain constant over time. HashMap is unsynchronized and Hashtable
is synchronized.
Source: Here
#include <algorithm>
#include <vector>
#include <fstream>
#include <map>
#include <iterator>
using namespace std;
int main() {
string str;
ifstream in("input.txt");
map<string, int> m;
if (in.is_open()) {
while(in >> str) {
m[str]++;
}
}
for(map<string, int>::iterator it = m.begin(); it != m.end(); it++) {
cout << (*it).first <<"\t" << (*it).second << endl;
}
}
input.txt
abc abc abc abc abc abc abc abcdef abc abcd
abc abc abc abc abc abc abc abcdef abc abcd
abc abc abc abc abc abc abc abcdef abc abcd
abc abc abc abc abc abc abc abcdef abc abcd
count words in a file and print words with their count more words file
output
ajay@ubuntu:~/workspace$ ./a.out
a 1
abc 32
abcd 4
abcdef 4
and 1
count 2
file 2
in 1
more 1
print 1
their 1
with 1
words 3
//Java method
import java.util.HashMap;
public class TestTest {
public static void main(String[] args){
String inputString = "abc abc abc abc abc abc abc abcdef abc abcd abc abc abc abc abc abc abc abcdef abc abcd" +
" abc abc abc abc abc abc abc abcdef abc abcd abc abc abc abc abc abc abc abcdef abc abcd" +
" count words in a file and print words with their count more words file";
HashMap<Object, Integer> myMap = new HashMap<Object, Integer>(){
@Override
public Integer put(Object arg0, Integer arg1) {
Integer i = super.get(arg0);
arg1 = i==null?1:i+1;
return super.put(arg0, arg1);
}
};
String[] splits = inputString.split(" ");
for(String s : splits){
myMap.put(s,1);
}
System.out.println(myMap);
}
}
Source: Here