Different Ways to Print First K Characters of a String in Java

A string is a class in Java that stores a series of characters enclosed within double quotes.Those characters are actually String-type objects. The string class is available in the?java.lang' package. Suppose we have given a string and a positive integer ?k'. Now, thejob is to print that string's first 'k' characters in Java. Also, check whether the length ofgiven string is less than or not, if so print the original string.

Java Program to Print First K Characters of the String

Let's understand the given problem with a few examples ?

Instance

String st1 = "TutorialsPoint";
String st2 = "Tutorial";

Assume we have the above strings with us and given k is 9. Then, the result would be ?

The first K characters of st1: Tutorials
The first K characters of st2: Tutorial

The length of string 1 is greater than 9, therefore we printed the first 9 characters. But, the length of 2nd string is less than 9, therefore we printed the whole string itself

Approach 1

• Create a user-defined method along with two parameters of String and integer type.

• Convert the given string into a character array and store it in ?chs[]'.

• We know that strings are immutable in Java therefore we need to create an object ?new_st' of the StringBuffer class to store characters of string into a character array

• Check the length of string using if-else block. If it is greater than k then append the first k characters to character array else print the given array.

• Now, in the main() method, declare and initialize strings and a positive integer k. Then, call the user-defined method using string and k as arguments

Example

The following example illustrates how we can retrieve the first K characters of a String using a user-defined method.

import java.util.*;
public class Kstring {
   public static void frstChar(String st, int k) {
      char chs[] = st.toCharArray(); // converting into character array
      StringBuffer new_st = new StringBuffer();
      if(st.length() > k) { // checking the length of string
         for(int i = 0; i < k; i++) {
            new_st.append(chs[i]); // appending characters to new string
         }
         System.out.println("The first K characters are: " + new_st.toString()); // printing the new string
      } else {
         System.out.println("K is greater than given String: " + st);
      }
   }
   public static void main(String args[]) {
      String st1 = "TutorialsPoint";
      String st2 = "Tutorial";
      int k = 9;
      System.out.println("The Original String: " + st1);
      System.out.println("The Original String: " + st2);
      
      // calling the method
      frstChar(st1, k);
      frstChar(st2, k);
   }
}

Output

The Original String: TutorialsPoint
The Original String: Tutorial
The first K characters are: Tutorials
K is greater than given String: Tutorial

Approach 2

• Declare and initialize a String and a positive integer ?k'.

• Now, using the if-else block check whether the length of String is greater than k or not. If it is greater than k, print the same number of characters of string using ?substring()' method otherwise print the whole string.

• The built-in method ?substring()' takes two arguments of integer type and prints the characters of specified string within the range of arguments.

Example

The following example illustrates how we can retrieve the first K characters of a String using an in-built method ?substring()'.

public class Kstring {
   public static void main(String args[]) {
      String st1 = "TutorialsPoint";
      int k = 9;
      System.out.println("The Original String: " + st1);
      
      if (st1.length() > k) { // checking the length of string
         System.out.println("The first K characters are: " + st1.substring(0, k));
      } else {
         System.out.println("The first K characters are: " + st1);
      }
   }
}

Output

The Original String: TutorialsPoint
The first K characters are: Tutorials

Conclusion

We started this article by defining String and understanding the problem statement for the Java program. Later, we discussed two example programs one with a user-defined methodand the other with a built-in method to print the first K characters of the given String.