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Showing posts with the label Java 8

How to convert Enum to List of String in Java 8?

Problem  How to convert Enum to List of String in Java 8?  Solution  Using the Java 8 Streams, its map and collect functions we can convert Enum to List of Strings  Code   import java.util.List; import; import; public class EnumToStringList { public enum Alpha { A,B,C,D; }  public static void main(String[] args) { List<String> strings = Stream.of(Alpha.values()).map(                                               Alpha::name).collect( Collectors.toList()); } }

Java - How to print Hibernate query parameters on console?

Introduction In this post, we will learn how to print Hibernate Query parameters using log4j. Requirments log4j-api-2.13.1.jar log4j-core-2.13.1.jar Step 1 Place the above two log4j jars inside the lib directory. For web applications, the lib directory is located inside the WEB-INF folder. Step 2 Create a file by the name of  log4j2.xml and place it inside your src folder. Step 3 Place the following XML code inside the  log4j2.xml file <configuration status="WARN"> <appenders> <console name="LogToConsole" target="SYSTEM_OUT"> <patternlayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"> </patternlayout></console> </appenders> <loggers> <logger additivity="false" level="debug" name="org.myapp"> <appenderref ref="LogToConsole"> &

Apache Maven - How to set network proxy settings?

In the following post, we learned how to install Apache Maven on Windows 10 How to install Apache Maven on Windows? If your development PC is behind a proxy network, you will not be able to add Java dependencies through Maven. Luckily Maven provides us with proxy settings. Add your network proxy to Maven's proxy settings STEP 1:  Navigate to your maven's directory and open conf folder E:\apache-maven-3.6.2\conf STEP 2:  Open settings.xml in your favorite text editor STEP 3: Uncomment the proxy tag inside proxies tag and add the values according to your network's proxy settings. <proxy>       <active>true</active>       <protocol>http</protocol>       <username>proxyuser</username>       <password>proxypass</password>       <host></host>       <port>80</port>       <nonProxyHosts>|</nonProxyHosts>     </proxy>

How to install Apache Maven on Windows 10?

Apache Maven is a Java tool that helps in building and managing the Java project. It is based on the concept of Project Object Modle(POM). It helps the Java developers to manage the project's JAR files in a central repository and those JAR files can be shared across the project. Maven project has the following objectives makes the build process easy provides a uniform build system  and many more In this post, we will learn how to install the Apache Maven on Windows (10). STEP 1: Download and install Java Download Java from . and install it. STEP 2: Download Apache Maven Download Apache Maven from  and extract it on your local machine like I have unzipped it to  E:\apache-maven-3.6.2 STEP 3: Set the JAVA_HOME environmental variable Right Click This PC ->  Properties -> Advanced system settings -> Environmental Variables Open Environmental Variables Click on N

Top 10 mostly asked Java String Interview Questions

Introduction String is the most widely used class in any language. In this post, we will explore String in Java context. This post will help you to understand the String in-depth and to answer String related questions in a Job interview. 1. What is String? String is a final class in Java and not a primitive data type like int, float, etc. It is defined in java.lang package and therefore available by default. 2. How to create objects of String? There are two ways to create String a. String literals String str = "abc"; b. Using new operator String str = new String("abc"); 3. Where is String stored in memory? String literals are stored in the String constant pool. A string is called immutable or constant i.e. once created then it can not be changed. Whenever we create a String using double quotes (String literal), Java looks into the String constant pool if an object with the same value is present, it returns the reference to that object

How to sort collections in Java 8?

Introduction In this post, we will explore different ways to sort Java collections in a certain order. Java platform provides a  Collections framework that represents a group of objects. All the Java classes those implement the Collection interface have by default implemented the sort method i.e. Collections.sort(list/set/Array) Java classes like String, Date, Integer, Double, Float, Long, Integer etc implements the Comparable interface by default. Java provides us with the following two interfaces to compare and sort the custom objects Comparable Interface  public interface Comparable<T> { public int compareTo(T o); } Java 8 also provides the built in Comparator.comparing method that returns an instance of Comparable. Comparator Interface public interface Comparator<T> { int compare(T o1, T o2); } In this post we will use the following student class for practice. public class Student{ public String name; public Integer age; public St

Hibernate 5.4.4 - How to fix hibernate depreciation warnings?

Problem Recently we migrated Hibernate to the latest version i.e. 5.4.4. Multiple depreciation warnings appeared in our code i.e. The type Query<R> is deprecated The method setString(String, String) from the type Query is deprecated The method uniqueResult() from the type Query is deprecated The method setBoolean(String, boolean) from the type Query is deprecated The method setLong(String, long) from the type Query is deprecated Solution Existing Change To import org.hibernate.Query; import org.hibernate. query .Query; query . setLong ( "serviceId" , serviceId ) ; query . setParameter ( "serviceId" , serviceId ); query . setBoolean ( "isDelete" ,Boolean. FALSE ) ; query . setParameter ( "isDelete" ,Boolean. FALSE ) ; query . setString ( "serviceNo" , serviceNo ) ; query . setParameter ( "serviceNo"

Java Example of Selection Sort

Introduction Selection sort is the simplest sorting algorithm in terms of implementation. Let's consider we have a list of elements i.e. {3, 9, 0, 5, 4 } a) Selection sort maintains two sublists, one sorted and initially empty and second unsorted sublist i.e. [ {}, {3, 9 , 0, 5 ,4 }] b) It searches for the minimum element (for ascending sort) OR for a maximum element( for descending sort) in the unsorted list in each step. Step 1 [ {0 }, {9,3,5,4}] Minimum element = 0 , swapped with 3 Step 2 Minimum element = 3 , swapped with 9 [{0,3) , {9,5,4} ] Step 3 Minimum element = 4 , swapped with 9 [{0,3,4} , {5,9}] Step 4 Minimum element = 5 , swapped with itself [{0,3,4,5}, {9}] Step 5 Minimum element = 9 , swapped with itself [{0,3,4,5,9}, {}] Worst Complexity: O(n*n) Best Complexity   : O(n * n) Imperative style implementation using Java 7 public class SelectionSortExample { private static int array[] = {3,9,0,5,4}; public static void mai

Java Bubble Sort Example

Introduction Bubble sort is the simplest sorting algorithm. It has the following steps a) Iterates through the list b) Compares the adjacent elements c) Swap the adjacent elements if they are in not in proper sorting order d) The list is traversed repeatedly unless the list is sorted Worst Complexity : O(n*n) Best Complexity    : O(n) Alternate name      : Sinking Sort Implementation using Simple Loops public class BubbleSortExample { private static int array[] = {0,5,2,6,3,1}; static int temp = 0; public static void main(String[] args) { bubbleSortAscending(); System.out.println("Ascending Sorted List"); for(int value : array) { System.out.print(value + " "); } bubbleSortDescending(); System.out.println("Descending Sorted List"); for(int value : array) { System.out.print(value + " "); } } private static void bubbleSortAscending() { for(int outer=0; outer<array.length; outer++) {

WARN orm.deprecation - HHH90000014: Found use of deprecated [] sequence-based id generator

Introduction  I upgraded Hibernate from version 4 to 5.4.4. Following warning was thrown by Hibernate WARN  orm.deprecation - HHH90000014: Found use of deprecated [] sequence-based id generator; use instead.  See Hibernate Domain Model Mapping Guide for details. http-nio-8080-exec-10 WARN  orm.deprecation - HHH90000014: Found use of deprecated [] sequence-based id generator; use instead.  See Hibernate Domain Model Mapping Guide for details. Old Code     @Id     @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_PERSON")     @SequenceGenerator(name = "SEQ_PERSON", sequenceName = "SEQ_PERSON_ID",allocationSize=1)     private Long id; SequenceGenerator is deprecated by Hibernate and we have to use either SequenceStyleGenerator or GenericGenerator instea

Hibernate 5.4.4 - select hibernate_sequence.nextval from dual

Exception http-nio-8080-exec-1 DEBUG hibernate.SQL - select hibernate_sequence.nextval from dual http-nio-8080-exec-1 WARN  spi.SqlExceptionHelper - SQL Error: 2289, SQLState: 42000 http-nio-8080-exec-1 ERROR spi.SqlExceptionHelper - ORA-02289: sequence does not exist org.hibernate.exception.SQLGrammarException: could not extract ResultSet at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert( at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert( Solution Default value for setting changed to true for 5.0, in previous versions it was set to false by default Add the following property to hibernate.cfg.xml <property name=""> false </property> OR Add the following property to the configuration properties.put("", " false &

Hibernate 5.4.4 - Instantiate an instance of SessionFactory

Introduction We will learn how to create an instance of SessionFactory using Hibernate 5.4.4 Code private static final SessionFactory sessionFactory; public static final String cfgFileLocation = "/hibernate.cfg.xml";  try {          StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder()                                            .configure( cfgFileLocation ).build();           Metadata metadata = new MetadataSources( standardRegistry )             .getMetadataBuilder()             .applyImplicitNamingStrategy( ImplicitNamingStrategyJpaCompliantImpl.INSTANCE )             .build();     sessionFactory = metadata.getSessionFactoryBuilder()           .build();     } catch (Throwable ex) {                  System.out.println( "exception" );         throw new ExceptionInInitializerError(ex);     } Following exceptions are resolved through the above code java.lang.IllegalArgumentException: org.hibernate.hql.intern

hibernate-release-5.4.4.Final - Required Jars

Introduction Hibernate (Object Relational Mapping framework) is an implementation of Java Persistence API (JPA) specification.   Required Jars for Hibernate 5.4.4 Following Jars resided inside the required folder are the mandatory jars required for Hibernate 5.4.4 antlr-2.7.7.jar byte-buddy-1.9.11.jar classmate-1.3.4.jar dom4j-2.1.1.jar FastInfoset-1.2.15.jar hibernate-commons-annotations-5.1.0.Final.jar hibernate-core-5.4.4.Final.jar istack-commons-runtime-3.0.7.jar jandex-2.0.5.Final.jar javassist-3.24.0-GA.jar javax.activation-api-1.2.0.jar javax.persistence-api-2.2.jar jaxb-api-2.3.1.jar jaxb-runtime-2.3.1.jar jboss-logging-3.3.2.Final.jar jboss-transaction-api_1.2_spec-1.1.1.Final.jar stax-ex-1.8.jar txw2-2.3.1.jar Hibernate 5.4.4 release is compatible with  Java 8 or 11  JPA 2.2 References

Jersey Framework Client - How to add HTTP Basic Authentication Header to HTTP Request?

Introduction In this tutorial, we will learn how to add HTTP basic authorization token to the HTTP request header. We will use Jersey Framework to consume RESTful web services. Read the following post if you want to learn how to secure web services using HTTP Basic Authentication Jersey Java Framework - How to add HTTP Basic Authentication to RESTful web services? Maven Dependencies <dependency>     <groupId>org.glassfish.jersey.core</groupId>     <artifactId>jersey-client</artifactId>     <version>2.29</version>  </dependency>  <dependency>     <groupId>org.glassfish.jersey.inject</groupId>     <artifactId>jersey-hk2</artifactId>     <version>2.29</version> </dependency> Basic Authentication is the most simple way to secure HTTP requests. It has the following format Authorization: Basic base64-encoding of username:password Jersey Client Jersy is the refe