Java Set Character in String

Java Set Character in String | In this blog, we will learn how to add a particular string to a string at a particular position. For instance, see the below example:-

1) String = “java”
Character to add to the end of string = ‘c’
Resultant string = “javac”

2) String = “now”
Character to add to the start of string = ‘k’
Resultant string = “know”

3) String = “clan”
Character to add = ‘e’
Position = 2
Resultant String = “clean”

Java Set Character in String at End

In this example, we will set the character at the end of the string. To add character at the end of the string we can use the concatenation operator (+). The concatenation operator can be used to add two strings. For this, we have to convert the character to a string. Let us see it through an example:-

public class Main {
   public static void main(String[] args) {

      String str = "HER";
      char ch = 'O';
      System.out.println("Before: " + str);
      str = str + Character.toString(ch);
      System.out.println("After: " + str);

      String str1 = "pin";
      char ch1 = 'e';
      System.out.println("Before: " + str1);
      str1 = str1 + Character.toString(ch1);
      System.out.println("After: " + str1);

      String str2 = "hone";
      char ch2 = 'y';
      System.out.println("Before: " + str2);
      str2 = str2 + Character.toString(ch2);
      System.out.println("After: " + str2);
   }
}

Output:-

Before: HER
After: HERO
Before: pin
After: pine
Before: hone
After: honey

The Character.toString() method is present in Java.Lang package, which takes character ‘c’ as a parameter and returns the converted string. The method details of the Character.toString() method is as follows:- String java.lang.Character.toString(char c).

Java Set Character in String at Beginning

This is also very similar to the previous example. In the previous program, we were adding a character at the end of the string but now we will add a character at the beginning of the string.

public class Main {
   public static void main(String[] args) {
      String str = "range";
      char ch = 'o';
      System.out.println("Before: " + str);
      str = Character.toString(ch) + str;
      System.out.println("After: " + str);

      String str1 = "other";
      char ch1 = 'm';
      System.out.println("Before: " + str1);
      str1 = Character.toString(ch1) + str1;
      System.out.println("After: " + str1);

      String str2 = "issue";
      char ch2 = 't';
      System.out.println("Before: " + str2);
      str2 = Character.toString(ch2) + str2;
      System.out.println("After: " + str2);

      String str3 = "our";
      char ch3 = 'p';
      System.out.println("Before: " + str3);
      str3 = Character.toString(ch3) + str3;
      System.out.println("After: " + str3);
   }
}

Output:-

Before: range
After: orange
Before: other
After: mother
Before: issue
After: tissue
Before: our
After: pour

Java Set Character in String at Between

In this code, we have used the substring() method to place the character at the required position. The substring() method is used to retrieve the substring in the particular index or from the particular index. The method details of the substring method are as follows:- public string substring(int position).

public class Main {
   public static void main(String[] args) {
      String str = "got";
      char ch = 'a';
      int position = 2;
      System.out.println("Before: " + str);
      str = str.substring(0, position) + Character.toString(ch) + 
            str.substring(position, str.length());
      System.out.println("After: " + str);

      String str1 = "cat";
      char ch1 = 'h';
      int position1 = 1;
      System.out.println("Before: " + str1);
      str1 = str1.substring(0, position1) + Character.toString(ch1) + 
            str1.substring(position1, str1.length());
      System.out.println("After: " + str1);
   }
}

Output:-

Before: got
After: goat
Before: cat
After: chat

Change Character In String Java

Instead of adding/setting a character in the string sometimes we need to change the character in the string. There are two possibilities while changing a character in string Java:-

  1. Change one character at a specific position/index.
  2. Replace all the occurrences of a particular character with another character in the given string.

Example of changing one character at a specific position/index:-
String = “Stronger”
Position to change the character = 3
New character to replace = ‘a’
Resultant string = “Stranger”

Example of replacing all the occurrences of a particular character with another character in the given string:-
String = “Java programming language”
Character to be replaced = ‘a’
New character = ‘X’
Resultant string = “JXvX ProgrXmming LXnguXge”

Java String Replace One Character at Given index

In this program, we will replace a particular character at the given index with another character. For this, we have to use the substring() method.

public class Main {
   public static void main(String[] args) {
      String str = "Stronger";
      char ch = 'a';
      int position = 3;
      System.out.println("Before: " + str);
      str = str.substring(0, position) + Character.toString(ch) + 
            str.substring(position+1, str.length());
      System.out.println("After: " + str);
   }
}

Output:-

Before: Stronger
After: Stranger

Java String Change Char All Occurrence

Now, we will see an example to replace all occurrences of a particular character in the given string. For this, we can use replace() or replaceAll method of the Java String class.

public class Main {
   public static void main(String[] args) {
      String str = "Java Programming Language";
      char oldChar = 'a';
      char newChar = 'X';
      System.out.println("Before: " + str);
      str = str.replace(oldChar, newChar);
      System.out.println("After: " + str);
   }
}

Output:-

Before: Java Programming Language
After: JXvX ProgrXmming LXnguXge

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