Replace character in string Java

Characters in Java

In the package of Java language, there is a container class called Character. A single field of type char is contained in a Character object. For manipulating characters, Character class gives us much useful class (i.e., static) methods. The Character function Object can be used to generate a Character object.

Creating character object

Character ch = new Character('a');

The preceding code generates a Character object with the char type 'a'. The Character class has only one function Object that takes a char data type argument.

When we send a simple character into a method that expects an object, then the compiler turns it to a Char class object automatically. Autoboxing and Unboxing are the terms for this feature.

Methods in the character class

• Boolean isLetter (char ch):-

This method tells us whether or not the supplied char value is a letter. If it's letter([A-Z],[a-z]), the procedure will return true; otherwise, it'll return false. As char to int is automatically typecasted in java, we may pass an ASCII value also as an input in place of a character.

Syntax:

boolean isLetter(char ch);

• Boolean isDigit(char ch):-

This method estimates whether or not the supplied char value(ch) is a digit. We can also pass an ASCII value as an input here.

Syntax:

boolean isDigit(char ch)

• Boolean isWhitespace(char ch):-

It checks to see if the given char value is white space. Space, tab, and newline are examples of whitespace.

Syntax:

boolean isWhitespace(char ch)

• boolean isUpperCase(char ch):-

It checks whether or not the provided char value is uppercase.

Syntax:

boolean isUpperCase(char ch);

• char toUpperCase(char ch):

It returns the provided char value's uppercase. If an ASCII value is supplied, the uppercase ASCII value will be returned.

Syntax:

char toUpperCase(char ch);

• boolean isLowerCase(char ch):-

It checks whether or not the provided char value is lowercase.

Syntax:

boolean isLowerCase(char ch);

• toString(char ch):-

It provides a String class object that represents the char value, which is a one-character string. We can't pass an ASCII value here.

Syntax:

String toString(char ch);

What is a 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 Builder:

The char value, which is a one-character string, is represented by a String class object. We can't use an ASCII value in this case.

Syntax:

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

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 represents fixed-length, immutable 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 a few ways to replace characters in a string:

 String Builder:

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.

Now take a look at an example:

public class GFG {


public static void main(String args[])
{
String str = "Hello World";
int index = 3;
char ch = 'F';
System.out.println("Original String = " + str);


StringBuilder string = new StringBuilder(str);
string.setCharAt(index, ch);
System.out.println("Modified String = " + string);
}
}

OUTPUT:

Original String: Hello World
New String: Hello World

String Buffer:

The StringBuffer class, like StringBuilder, provides a predefined method 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. Thread-safe StringBuffer When compared to StringBuffer, StringBuilder is faster, but it is not thread-safe.

Example:

public class GFG {


public static void main(String args[])
{
String str = “Hello World";
int index = 6;
char ch = 'F';
System.out.println("Original String = " + str);


StringBuffer string = new StringBuffer(str);
string.setCharAt(index, ch)
System.out.println("Modified String = " + string);
}
}

OUTPUT:

Original String: Hello World
New String: Hello World