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Tuesday, 13 March 2018

What is Hashmap in Java? Hashmap vs HashTable


HashMap in java


Hi all, in this demo i will describe about HashMap in java.


Map Interface.
public interface Map
An object that maps key to values. A map cannot contain duplicate keys;each key can map to at most one value.
This interface takes the place of the Disctionary class, which was a totally Abstract Class rather than an interface.

HashMap is important for selenium as well as for interview also.
hashMap is a Map based collection class that is used for storing Key & Value(associated with keys).
1).It is donated as HashMap.
2).Hashmap contains only unique elements.
3).Hashmap may have only one null key and multiple null values
4). Hashmap maintains no order.

Here is the example of HashMap in Java.

import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class hashmapdemo
{
public static void main(String args[])
{
hashmapdemo obj = new hashmapdemo();
obj.g();
}
public void g()
{
Map< String, Integer > record = new HashMap<>();
record.put("Anjana", 26);
record.put("Silpi", 27);
record.put("Heena", 28);
record.put("Adhiraj", 29);
System.out.println(record.get("Heena"));
Set<String> keys = record.keySet();
for(String i : keys)
{
System.out.println(i + ":" +record.get(i));
}
}
}

Output :

28
Adhiraj:29
Anjana:26
Silpi:27
Heena:28





TreeMap in Java

TreeMap is Red-Black tree based NavigableMap implementation. It is sorted according to the natural ordering of its keys.
TreeMap class implements Map interface similar to HashMap class.
The main difference between them is that HashMap is an unordered collection while TreeMap is sorted in the ascending order of its keys.
TreeMap is unsynchronized collection class which means it is not suitable for thread-safe operations until unless synchronized explicitly.

Here is the example of TreeMap in Java.

import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
public class hashmapdemo
{
public static void main(String args[])
{
hashmapdemo obj = new hashmapdemo();
obj.g();
}
public void g()
{
//Map<String, Integer> record = new HashMap<>();
TreeMap<Integer, String> record = new TreeMap<>();
record.put(26, "Anjana");
record.put(28, "Heena");
record.put( 29, "Adhiraj");
record.put(27, "Silpi");
System.out.println(record.get(28));
for(Integer i : record.keySet())
{
System.out.println(i + ":" +record.get(i));
}
}
}


Output :

Heena
26:Anjana
27:Silpi
28:Heena
29:Adhiraj



HashMap vs TreeMap

Saturday, 3 March 2018

for each loop in java with example


for Each loop in java :
Hi all, in this demo i will describe about for-each loop in java.

This loop is important for selenium as well as for interview also.
So as the name says when we want to perform some operation with each element of the list or collection or array, then we use this loop.
The Syntax of the loop is :
for(data_type variable_name : array|collection)
{
}
it will get more clear when we describe it through an example :

Example of for-each loop in java


public class foreach
{
public static void main(String args[])
{
int arr[] = {10, 20, 30, 44};
for(int x : arr)
{
System.out.println("Your number is :" + x);
}
}
}
---------------------------------------------------------------------------
Now, Suppose you are working in some selenium project, and have create a WebElement list then, you can perform operation with each element using for -each loop

For Each Loop in selenium Example :
import java.util.List;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.Test;

public class foreach_selenium
{
WebDriver driver;
@BeforeTest
public void g() throws InterruptedException
{
System.setProperty("webdriver.chrome.driver", "D:\\Selenium\\Complete selenium\\ChromeDriver\\chromedriver.exe");
driver = new ChromeDriver();
driver.manage().window().maximize();
driver.navigate().to("http://www.way2testing.com");
Thread.sleep(3000);
}
@Test
public void h()
{
List list = driver.findElements(By.cssSelector("#post-body-751561208295527719>div>div>table>tbody>tr>td>a"));
System.out.println("Your total list elements are :" +list.size());
for(WebElement wb : list)
{
System.out.println(wb.getText());
}
}
}


Output :

Manual Testings Introduction
Definitions of Manual Testings
Defect Clustering in Software Testing
Bug Life Cycle & Reviews
Level of Testing
TEST CASE, TEST PLAN & RTM
Manual test Cases for Pen
Manual test cases for Email
ISTQB Practice set
Important Unix Command for Software Tester
Testings Myth
Agile Methodology
Windows & Linux Shortcut keys
Test Strategy in Software Testing
Finance Testing Basics
Mobile Test
Effort Estimation Technique
Java Script Basics
How to test Login page & Date fields manually
Technical Tips
Function in Javascript
Discussion Forum
Download e_Books
Professional Ethics
Aptitude Tricks
English Speaking Tutorials