Different ways to print first K characters of 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, the job is to print that string's first 'k' characters in Java. Also, check whether the length of given 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 −

Example

String st1 = “TutorialsPoint”;
String st2 = “Tutorial”;

Suppose we already have the above string and the given k value is 9. Then, the result will be −

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

The length of string 1 is greater than 9, so we print the first 9 characters. However, the length of string 2 is less than 9, so we print the entire string itself

method one

• 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

• Use an if-else block to check the length of a string. If the length is greater than k, append the first k characters to the character array, otherwise print the given array.

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

with the string and k as arguments

Example

The following example illustrates how to use user-defined methods to retrieve the first K characters of a string.

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()' accepts two parameters of integer type and prints the characters in the specified string within the parameter range.

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

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