Awesome explanation of Strings in Java

What do you mean by String?

Strings are a collection of characters that are commonly used in Java programming. Strings are regarded as objects in the Java programming language.

“String” is a Java platform class that allows you to construct and handle strings.

Creating Strings

The normal way to create a string in Java is to simply write:-

String s = “Hello World”;

The compiler constructs a String object with the value "Hello world!" whenever it detects a string phrase in your code.

String objects cannot be made by using the new keyword and a function Object, just like any other object. The String class provides 11 constructors that allow you to set the string's initial value from a variety of sources, including an array of characters.

Another way to create a string is:-

String s = new String (“Hello World”);

String Buffer:-

StringBuffer is a String companion class that provides a lot of the same functionality as strings. StringBuffer shows growable and writable character sequences, whereas string shows fastened-length, unchangeable character sequences.

Syntax:

StringBuffer s = new StringBuffer("Hello World");

String Tokenizer:-

The StringTokenizer class in Java is used to tokenize a string.

String Joiner:-

String Joiner is a java.util package class that is used to build a sequence of characters divided by a delimiter and optionally starting with a transferred prefix and finishing with a transferred suffix.

Syntax:

public StringJoiner(CharSequence delimiter);

As we study in the above part, we have sufficient knowledge about replacing a character in a string

So, there are three ways to replace a character in a string:

StringBuilder:

In contrast to the String Class, the StringBuilder class includes a built-in function for this — setCharAt (). By calling this function and giving the character and the index as parameters, you can replace the character at a given index.

Syntax:

StringBuilder str = new StringBuilder();
str.append("GFG");

Null and empty string in Java:-

NULL  STRING :- A string that contains no value in it, simply called a Null String.

We can use the null string in Java in the following way:

String a = null;

“a” is a null string in this case. The attribute does not relate to any memory location in a heap when the null is assigned to the string variable.

EMPTY STRING:- An empty string is a type of string with no characters and a very well-defined length of 0. On an empty string, we can do all of the string operations.

Blank String

If we additionally want to identify blank strings, we may use String#trim to accomplish this. Before performing the check, it will remove any leading and trailing whitespaces.

We can use an empty string in Java in the following way:

String x = "";

“x” is an empty string in this case. The empty string expresses that the attribute corresponds to a memory location of a string in a clump when we delegate it to the string variable.

Different ways to find a string is null or empty:

• String length method:-

The Empty () method refers to the String class's length () method. Because the is Empty () method isn't accessible in Java 6 and below, we can use the length () method instead:

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 RETURNS TRUE IF LENGTH IS 0 OTHERWISE IT RETURNS 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:

The static utility function isNullOrEmpty(String) in Guava's Strings class gives true if the provided string is null or empty.

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:

The String.isEmpty() function is recommended for checking an empty string in Java starting with Java 7. If the string is null, a null verification should come before the method call to avoid a NullPointerException.

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

OUTPUT:

True

Apache:

 StringUtils.isEmpty(String) in the Apache Commons Lang library tests whether a string is empty or null. It also has a function called StringUtils.isBlank(String), which looks for whitespace.

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