JAVA
Java Collections class
Java collection class is used exclusively with
static methods that operate on or return collections. It inherits Object class.
|
Method |
Description |
|
static
<T> boolean addAll(Collection<? super T> c, T... elements) |
It is
used to add all of the specified elements to the specified collection. |
|
static
<T> Queue<T> asLifoQueue(Deque<T> deque) |
It is
used to return a view of a Deque as a Last-In-First-Out (LIFO) Queue. |
|
static
<T> int binarySearch(List<? extends T> list, T key,
Comparator<? super T< c) |
It is
used to search the specified list for the specified object using the binary
search algorithm. |
|
static
<E> List<E> checkedList(List<E> list, Class<E> type) |
It is
used to return a dynamically typesafe view of the specified list. |
|
static
<E> Set<E> checkedSet(Set<E> s, Class<E> type) |
It is
used to return a dynamically typesafe view of the specified set. |
|
static
<E> SortedSet<E>checkedSortedSet(SortedSet<E> s,
Class<E> type) |
It is
used to return a dynamically typesafe view of the specified sorted set |
|
static
void reverse(List<?> list) |
It is
used to reverse the order of the elements in the specified list. |
Collections example program
import java.util.*;
public class CollectionsExample{
public static void main(String[] args) {
List<Integer> list=new ArrayList<Integer>();
list.add(46);
list.add(67);
list.add(24);
list.add(16);
list.add(8);
list.add(12);
System.out.println("Value of maximum element from the collection:"+Collections.max(list));
}
}
OUTPUT:
value of maximum element from the collection: 67
Java Comparable interface
Java Comparable interface is used to order
the objects of user-defined class.This interface is found in java.lang package
and contains only one method named compareTo(Object). It provide single sorting
sequence only i.e. you can sort the elements on based on single data member
only. For example it may be rollno, name, age or anything else.
compareTo(Object
obj) method
public int compareTo(Object obj): is
used to compare the current object with the specified object.
We can sort the elements of:
1.
String objects
2.
Wrapper class objects
3.
User-defined class objects
Java Comparator interface
Java Comparator interface is used to
order the objects of user-defined class.
This interface is found in java.util package
and contains 2 methods compare(Object obj1,Object obj2) and equals(Object
element).
It provides multiple sorting sequence i.e.
you can sort the elements on the basis of any data member, for example rollno,
name, age or anything else.
compare() method
public int compare(Object obj1,Object obj2): compares the first object with second object.