First, use the getenv() method to get the environment variables −System.out.println("PATH = " + System.getenv("PATH"));Now, get the key and value. Loop through to get the list of environment variables −Map e = System.getenv(); for (Iterator i = e.entrySet().iterator(); i.hasNext();) { Map.Entry mapEntry = (Map.Entry) i.next(); System.out.println(mapEntry.getKey() + " = " + mapEntry.getValue()); }The following is an example to retrieve environment variables with Map Collection −Example Live Demoimport java.util.Iterator; import java.util.Map; public class Demo { public static void main(String args[]) { System.out.println("PATH = " + System.getenv("PATH")); ... Read More

Use the subset() method to get elements from a limit. At first, create NavigableSet and add elements −NavigableSet set = new TreeSet(); set.add(10); set.add(25); set.add(40); set.add(55); set.add(70); set.add(85);Now, use the subset() method −set.subSet(40, 85)The following is an example to implement subset() method of Java NaviagbleSet class −Example Live Demoimport java.util.NavigableSet; import java.util.TreeSet; public class Demo { public static void main(String[] args) { NavigableSet set = new TreeSet(); set.add(10); set.add(25); set.add(40); set.add(55); set.add(70); set.add(85); set.add(100); System.out.println("Returned Value = " + set.subSet(40, 85)); } }OutputReturned Value = [40, 55, 70]

The lower() method of NavigableSet returns the greatest element strictly less than the given element i.e. 35 here −lower(35);The following is an example to implement the lower() method in Java −Example Live Demoimport java.util.NavigableSet; import java.util.TreeSet; public class Demo { public static void main(String[] args) { NavigableSet set = new TreeSet(); set.add(10); set.add(25); set.add(40); set.add(55); set.add(70); set.add(85); set.add(100); System.out.println("Returned Value = " + set.lower(35)); } }OutputReturned Value = 25

All the elements in a collection of objects can be traversed using the Enumeration interface. The method hasMoreElements( ) returns true if there are more elements to be enumerated and false if there are no more elements to be enumerated. The method nextElement( ) returns the next object in the enumeration.A program that demonstrates this is given as follows −Example Live Demoimport java.util.Enumeration; import java.util.Vector; public class Demo { public static void main(String args[]) throws Exception { Vector vec = new Vector(); vec.add("John"); ... Read More

A stack can be implemented using a LinkedList by managing the LinkedList as a stack. This is done by using a class Stack which contains some of the Stack methods such as push(), top(), pop() etc.A program that demonstrates this is given as follows −Example Live Demoimport java.util.LinkedList; class Stack { private LinkedList l = new LinkedList(); public void push(Object obj) { l.addFirst(obj); } public Object top() { return l.getFirst(); } public ... Read More

The subList of a LinkedList can be obtained using the java.util.LinkedList.subList(). This method takes two parameters i.e. the start index for the sub-list(inclusive) and the end index for the sub-list(exclusive) from the required LinkedList. If the start index and the end index are the same, then an empty sub-list is returned.A program that demonstrates this is given as follows −Example Live Demoimport java.util.LinkedList; import java.util.List; public class Demo { public static void main(String[] args) { LinkedList l = new LinkedList(); l.add("John"); ... Read More

An element can be removed from a stack using the java.util.Stack.pop() method. This method requires no parameters and it removes the element at the top of the stack. It returns the element that was removed.A program that demonstrates this is given as follows −Example Live Demoimport java.util.Stack; public class Demo { public static void main (String args[]) { Stack stack = new Stack(); stack.push("Apple"); stack.push("Mango"); stack.push("Guava"); stack.push("Pear"); ... Read More

A stack in Java is a data structure that is used for storing elements. It follows the LIFO (Last In, First Out) principle. If we add an element to the stack last, it will be added at the top of the stack (thus it will be the first one to be picked). If we add another element to the stack, the previously added element will be pushed down, and the new element will be added at the top. We can not access previously added elements until we remove the top element.Add an Element to a Stack in Java In ... Read More

To get the element ordered first i.e. the first element in TreeSet, use the first() method.Create a TreeSet and add elements to it −TreeSet set = new TreeSet(); set.add("65"); set.add("45"); set.add("19"); set.add("27"); set.add("89"); set.add("57");Now, get the first element −set.first()The following is an example to get the element ordered first in TreeSet −Example Live Demoimport java.util.*; public class Demo { public static void main(String args[]) { TreeSet set = new TreeSet(); set.add("65"); set.add("45"); set.add("19"); ... Read More

First, create a TreeSet and add elements to it −TreeSet set = new TreeSet(); set.add("65"); set.add("45"); set.add("19"); set.add("27"); set.add("89"); set.add("57");Now, sort it in ascending order, which is the default −Iterator i = set.iterator(); while(i.hasNext()){ System.out.println(i.next()); }If you want to sort in descending order, then use the descendingIterator() method −Iterator j = set.descendingIterator(); while(j.hasNext()) { System.out.println(j.next()); }The following is an example to sort items in a TreeSet in ascending and descending order −Example Live Demoimport java.util.*; public class Demo { public static void main(String args[]){ TreeSet set ... Read More