Java Tutorial

Java Tutorial Java Features C++ vs Java Java History Java Hello World Java Development Kit Java Runtime Environment Java Virtual Machine Difference between JDK, JRE, and JVM Memory Areas in Java Java Operators Java Keywords Primitive Data Types Variables

Java Loops

Java Do While Loop Java While Loop Java For Loop Java Enhanced For Loop

Java Programs

Java Basic Programs Factorial Program in Java Fibonacci Series Program in Java Prime Number Program in Java Palindrome Number Program in Java Armstrong Number Program in Java Anagram Program in Java Pattern Programs in Java Calculator Program in Java Leap Year Program in Java Addition Program in Java Number Pattern Programs in Java Star Pattern Programs in Java Package Program in Java Pyramid Program in Java Sorting Program in Java String Palindrome Program in Java Even Odd Program in Java For Loop Program in Java If Else Program in Java Switch Case Program in Java GCD Program in Java LCM Program in Java Hello Program in Java Matrix Program in Java Menu Driven Program in Java Series Program in Java Client Server Program in Java Swapping Program in Java Pig Latin Program in Java Tower of Hanoi Program in Java Recursion Program in Java Matrix Multiplication Program in Java Perfect Number Program in Java Classes and Objects in Java Example Programs String Programs in Java Array Programs in Java Constructor Program in Java Inheritance Program in Java Abstract class Program in Java Interface Program in Java Encapsulation Program in Java Polymorphism Program in Java Exception Handling Program in Java Multithreading Program in Java Thread Program in Java Collection Programs in Java ArrayList Program in Java Stack Program in Java Applet Program in Java Swing Program in Java JDBC Program in Java How to run Java program in command prompt How to run Java program in Eclipse Program to find and replace characters on string in java Program to find the duplicate characters in a string Program to check whether a given character is present in a string or not Java Program to Print Permutations of String Java program to find frequency of characters in a string Java Program to remove duplicate characters in a string

Java Sorting

Sorting Algorithms in Java Merge Sort in Java Quick Sort in Java Bubble Sort in Java Insertion Sort in Java Selection Sort in Java Heap Sort in Java Radix Sort in Java Topological Sort in Java Bucket Sort in Java Counting Sort in Java

Java OOPs Concepts

OOPs - Object Oriented Programming Objects and Classes in Java Methods in Java Java Naming Conventions Constructors in Java Java this keyword Java static keyword Inheritance in Java Aggregation in Java Java super keyword Constructor Chaining and Constructor Overloading Java Polymorphism Static and Dynamic Binding in Java Java Abstraction Abstract class in Java Interface in Java Difference between Abstract class and Interface Java final keyword Packages in Java Access Modifiers in Java Java Wrapper classes Java Numbers Java Characters Java Integer Java Boolean Java Arrays Java Command Line Arguments Java strictfp Keyword Java Math

Java Strings

Java Strings Java String Methods StringBuilder in Java StringBuffer in Java Java Regular Expressions StringBuffer vs StringBuilder String vs StringBuffer String vs StringBuilder String Manipulation in Java Java String Concatenation How to Reverse a String in Java String Array in Java How to Compare Two Strings in Java How to Concatenate Two Strings in Java Why String in Immutable in Java Java.lang.NumberFormatException for Input String String Pool in Java Java Generate Random String How to take String Input in Java Java String Interview Questions

Java Exceptions

Exception Handling in Java Java try catch Java throw Java throws Difference between throw and throws Java finally Java Custom Exception Java Exception Propagation

Garbage Collection

Automatic Resource Management in Java Java Garbage Collection Java finalize() Java gc() Difference between final, finally and finalize

Multithreading

Multithreading in Java Process and Thread in Java Basic Terms in Multithreading Java Thread creation Thread Scheduler in Java Java Thread class DeadLock in Java

Java IO

Java IO Java Read File Java file Reader Java Buffer Reader Java file Writer Java BufferedWriter Java InputStreamReader Scanner in Java Java StringReader Java StringReader Class Java PrintWriter Java File Java Read File Line By Line Java FileInputStream Java FileOutputStream Java Create File Java Delete File Java Open File Java Read File to String Java copy file Java Read JSON file Jar File in Java Java FileNotFoundException

Serialization

Java Serialization Java transient

Networking

Java Network Programming Java Socket Programming Java URL Java URLConnection HttpURLConnection in Java Java InetAddress Java DatagramSocket and Java DatagramPacket

AWT

Java AWT

Swing

Swing in Java

Java Collections

Collections in Java Java List Interface ArrayList in Java LinkedList in Java Vector in Java Stack in Java ArrayList vs LinkedList in Java ArrayList vs Vector in Java Java Set Interface HashSet in Java LinkedHashSet in Java TreeSet in Java Java Queue Interface PriorityQueue in Java ArrayDeque in Java Java Map Interface HashMap in Java LinkedHashMap in Java TreeMap in Java Dictionary in Java Hashtable in Java Properties in Java Collections class in Java Java Comparable Java Comparator Comparable vs Comparator in Java

Java Generics

Generics in Java

Java Annotations

Annotations in Java

Java JDBC

Java JDBC Tutorial JDBC Architecture Types of JDBC Drivers JDBC vs ODBC Java Database Connectivity with MySQL Statements in java Prepared statement in Java Resultset in java Java ResultSetMetaData DatabaseMetaData in Java Callable Statement in Java Transaction Management in java

Java Differences

Java vs JavaScript Python vs Java Kotlin vs Java Java vs C++ C# vs Java Static vs Non-static in Java C vs Java int vs Integer in Java Stack vs Heap in Java Java Array vs ArrayList

How to

How to run Java program How to set path in Java How to check the Java version in cmd How to install Java in Windows 10 How to run Java program in cmd How to add double quotes in a string in Java How to convert list to String in Java How to call a method in Java How to sort an array in Java How to iterate HashMap in Java How to write Java program How to create an array in Java How to create a package in Java How to generate random numbers in Java How to input String in Java How to create thread in Java How to find length of String in Java How to sort a string in Java How to use scanner in Java How to achieve multiple inheritance in Java How to find the length of an Array in Java How to run Java program in Eclipse How to call a function in Java How to create array of objects in Java How to create custom exception in Java How to import packages in Java How to run applet Program in Java How to take Array Input in Java How to achieve abstraction in Java How to call static method in Java How to compare characters in Java How to initialize string array in Java How to Install Java on MAC How to run java program in ubuntu How to find characters with the maximum number of times in a string java How to Set Java_home in Linux How to Split the String in Java with Delimiter How to Split String by Comma in Java How to remove special characters from String in Java How to remove last character from String in Java

Java 8 Features

Java 8 Features Lambda Expressions in Java Functional Interface in Java Streams in Java Java Base64 Encoding and Decoding Parallel Arrays Sort in Java

Java 9 Features

Java 9 Tutorial Java 9 Try With Resources Java 9 Interface Private Method

Java Servlet Tutorial

Java Servlets Tutorial

Java JSP Tutorial

Java JSP Tutorial

Hibernate Tutorial

Hibernate Tutorial

Spring Tutorial

Spring Tutorial

Spring MVC Tutorial

Spring MVC Tutorial

Jenkins Tutorial

Jenkins Tutorial

Java Math Methods

Math.abs() Math.acos() Math.addExact() Math.asin() Math.atan () Math.atan2() Math.cbrt() Math.ceil() Math.copysign() Math.cos() Math.cosh() Math.decrementExact() Math.exp() Math.expm1() Math.floor() Math.floorDiv() Math.floorMod() Math.getExponent() Math.hypot() Math.IEEEremainder() Math.incrementExact() Math.log() Math.log10() Math.log1p() Math.max() Math.min() Math.multiplyExact() Math.multiplyFull() Math.negateExact() Math.nextAfter() Math.nextDown() Math.nextUp() Math.pow() Math.random() Math.rint() Math.round() Math.scalb() Math.signum() Math.sin() Math.sinh() Math.sqrt() Math.subtractExact() Math.tan() Math.tanh() Math.toDegrees() Math.toIntExact() Math.toRadians() Math.ulp()

Java String Methods

toCharArray() copyValueOf() endsWith() equals() equalsIgnoreCase() format() getBytes() getChars() hashCode() indexOf() intern() isEmpty() join() lastIndexOf() length() replace() replaceAll() replaceFirst() split() startsWith() subSequence() substring() toLowerCase() toUpperCase() trim() valueOf()

Java Conversion

Java Convert String to int Java Convert int to String Java Convert String to long Java Convert long to String Java Convert String to float Java Convert float to String Java Convert String to double Java Convert double to String Java Convert String to Date Java Convert Date to String Java Convert String to Object Java Convert Object to String Java Convert String to char Java Convert char to String Java Convert int to long Java Convert long to int

Misc

Functional Interfaces in Java Singleton class in Java Awesome explanation of Strings in Java Object class in Java Static class in Java All the important string methods in Java String Handling Method in Java What are Array strings in Java Advantages and Disadvantages of Strings in Java Big Decimal class in Java Class definition in Java Char and String differences in Java Difference between String, StringBuffer and StringBuilder in java Replace character in string Java String Coding Interview Questions in Java What is String in Java? String isnullorempty in Java String Matches in Java Trim Method in String Java Bean class in Java Libraries in Java Arithmetic Operations on String in Java Convert Char array to string in java Check whether Java is installed or not How to calculate time difference in Java How to stop execution after a certain time in Java Jagged Array in Java Java ArraylistRemove() Time Complexity Java Swing Time Picker Zigzag Array in Java Array and String based questions in Java Array and String with Examples in Java Best Practices to use String Class in Java What is string in Java why it's immutable Java String Java String Inbuilt functions Java String Matches vs Contains Sum of digits in string in java Check the presence of Substring in a String in java Java import packages Interfaces and Classes in Strings in Java Maximum length of string in java Hidden classes in Java Class memory in Java public static void main string args meaning in java Reverse a String in Java String Concatenation in Java Difference between String and Char Array in Java Buffer reader to read string in Java

Array and String with Examples in Java

Array in Java:

An array in Java is a group of variables with similar types that have a common name. The arrays used in Java differ from those used in C/C++.

Key points

  • Java uses dynamically allocated arrays extensively.
  • Arrays are objects in the Java programming language, and the object attribute length may be used to estimate their length ().
  • The array's variables are ordered, and each variable's index starts at 0.
  • A Java array can be used with a static field, a local variable, or a method parameter.
  • The Cloneable and java.io interfaces are implemented by each array type that may be serialized.
  • The immediate superclass of the common array type is Object.
  • Object (or non-primitive) class references and basic data types like int and char can both be stored in arrays. The common values of fundamental data kinds are stored in adjacent memory regions. The original objects for class objects are stored in a heap region.

One Dimensional Array:

Normal declaration of one dimensional array is

type var-name[];
OR
type[] var-name;

The type and name of an array can both be specified separately. The word "type" denotes the nature of the elements in the array. The element type determines the data type for each array element. We may construct an array of numerous primitive data types, including char, float, double, and so on, as well as user-defined data types, in a manner similar to how we would generate an array of integers (objects of a class). As a result, the element type of an array determines the kind of data that it may include. Making an Array Instantiate:

Only a reference to an array is produced when it is defined.

An array must first be made in the way described below in order to produce data from it or add memory to it.

The following is how new is expressed for one-dimensional arrays:

var-name = new type [size];

The array's size is determined by the number of elements, the kind of data being allocated, and var-name, the name of the array variable connected to the array. You must provide the type and quantity of the elements to be allocated when allocating an array using new.

Declaring an Array>>  int intArray[];
Allocating memory to Array>> intArray = new int[20];

Point to Remember:

When new allocates an array, its default values are 0 for numeric types, false for boolean types, or null for all other types (for reference types). Use Java's default array values.

Getting an array requires a two-step process. Make a variable of the necessary array type first. Use new and then assign it to the array variable to create a memory for the array. Java employs dynamic allocation for all arrays as a result.

Array Literal:

Array literals can be utilized when the array's size and its variables are known.

int[] intArray = new int[]{ 1,2,3,4,5,6,7,8,9,10 }; 

The length of this array defines the length of the newly constructed array, which need not be written in Java's most current iterations.

Array program using for loop

class TAE{
public static void main (String[] args){		
// declares an Array
int[] arr;		
// allocating memory
arr = new int[5];	
// initialize the first element of an array
arr[0] = 5;		
// initialize the second element of an array
arr[1] = 10;
//so on...
arr[2] = 15;
arr[3] = 20;
arr[4] = 25;		
// accessing the elements of the specified array
for (int i = 0; i < arr.length; i++)
System.out.println("Element at index " + i +" : "+arr[i]);		
}
}

Output:

Element at index 0 : 5
Element at index 1 : 10
Element at index 2 : 15
Element at index 3 : 20
Element at index 4 : 25








Arrays of Object:

Student[] arr = new Student[5]; //student is a user-defined class

Each of the five memory spaces in the studentArray, one for each student class, may store the addresses of five Student objects. The Student class's Object() function must be used to construct the Student objects, and the references to those objects must be allocated to the elements of the array as shown below.

Student[] arr = new Student[5];


class Student{
public int roll_no;
public String name;
Student(int roll_no, String name){
this.roll_no = roll_no;
this.name = name;}
}
// Elements of the array 
public class TAE{
public static void main (String[] args){
// declares an Array 
Student[] arr;
// allocating memory
arr = new Student[5];
// initializing first element 
arr[0] = new Student(1,"Ajay");
// initializing second element
arr[1] = new Student(2,"Kaishav");
// so on...
arr[2] = new Student(3,"Rakesh");
arr[3] = new Student(4,"Zaid");
arr[4] = new Student(5,"Kasim");
// accessing the elements of specified array
for (int i = 0; i < arr.length; i++)
System.out.println("Element at " + i + " : " +
arr[i].roll_no +" "+ arr[i].name);
}
}

Output:

Element at 0 : 1 Ajay
Element at 1 : 2 Kaishav
Element at 2 : 3 Rakesh
Element at 3 : 4 Zaid
Element at 4 : 5 Kasim


String in Java

Strings are a collection of characters that are often used in Java programming. In Java, strings are referred to as objects.

The Java platform class "String" allows you to create and manage strings.

A null and empty string in Java:-

NULL  STRING:- The term "Null String" refers to a string that is empty.

Java allows us to use null strings in the following ways:

Empty String: When the null is assigned to the string variable, the attribute has no connection to any heap memory address.

NOTHING STRING

An empty string is a string type with no characters and a clearly specified length of zero. On an empty string, we may do all string operations.

Blank String

String#trim can be used to identify blank strings if we also wish to do that. Any leading and trailing whitespaces will be eliminated before running the check.

Java allows us to use empty strings in the following ways:

String x = "";

The string "x" is empty in this case. When we give an attribute to the string variable, the empty string indicates that the attribute corresponds to a memory location of a string in a clump.

Ways to determine whether a string is empty or null

Calculating string length:

The length () function of the String class is referred to in the Empty () method. We can use the length () method in place of the is Empty () method as Java 6 and earlier don't support it:

public class IsEmpty{
public static void  main(String args[]){
String s1=””;
String s2=”helloworld”;
String s3=”star”;
System.out.println(s1.isEmpty());  // Command to print
System.out.println(s2.isEmpty());
System.out.println(s3.isEmpty());
}}
// It gives true when the length is zero otherwise it throws false


Output:

True	
False
False

String Equals Method:

class Main
{
private static String EMPTY = ""; // Empty class
public static void main(String[] args)
{
String str = ""; //Empty Class
System.out.println(str == null || str.equals(EMPTY));
System.out.println(str == null || EMPTY.equals(str));
}
}

Output

True
True

Guava Library Method:

If the supplied string is empty or null, the static utility function isNullOrEmpty(String) in Guava's Strings class returns true.

class Main
{
public static void main(String[] args)
{
System.out.println(Strings.isNullOrEmpty(""));   //empty class
System.out.println(Strings.isNullOrEmpty(null));    //null class
System.out.println(Strings.isNullOrEmpty("Hello"));
}
}

Output

True
True
False


Empty Method: Starting with Java 7, it is advised to use the String.isEmpty() function to determine whether a string is empty. To prevent a NullPointerException, a null verification should come before the method call if the string is null.

class Main{
public static void main(String[] args)
{
String str = ""; //Empty string
System.out.println(str == null || str.isEmpty());
}
}

OUTPUT:

 True

Apache:

The Apache Commons Lang library's StringUtils.isEmpty(String) function determines whether a string is empty or null. Additionally, it has a function that searches for whitespace called StringUtils.isBlank(String).

class Main{
public static void main(String[] args)
{
System.out.println(StringUtils.isEmpty(""));  // Empty
System.out.println(StringUtils.isEmpty(null)); // Null
System.out.println(StringUtils.isEmpty("Java")); // String
System.out.println(StringUtils.isBlank(" "));  // Blank
}
}

OUTPUT:

True
True
False
True



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