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

  • Last Updated : 30 Aug, 2020

Given a string str and a positive integer k, the task is to write a Java program to print the first k characters of the string. If the length of the string is less than k then print the string as it is.

Examples:

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Input: str = “GeeksForGeeks”, k = 5

Output: Geeks



Explanation: The first k characters of the given string is ‘Geeks’.

Input: str = “Geeks”, k = 6

Output: Geeks

Explanation: The length of the given string is less than k. Therefore, we print the string as it is.

Method 1: Using string length

  1. Get the string and a positive integer k to print the first k characters of the string.
  2. Check if the string is null or empty then return null.
  3. Check if the string length is greater than k then get the first k characters of the string using str.substring(0, k).
  4. If the string length is less than k then return the string as it is.
  5. Now, print the first k characters of the string.

Below is the implementation of the above approach:

Java




// Java program to print first k
// characters of the string
  
class GFG {
      
    // Function to print first k
    // characters of the string
    public static String 
      firstKCharacters(String str, int k)
    {
          
        // Check if the string is empty
        // or null then return null
        if (str == null || str.isEmpty())
            return null;
          
        // Check if the string length
        // is greater than k, then
        // get the first k characters 
        // of the string, otherwise
        // return the string as it is
        if (str.length() > k)
            return str.substring(0, k);
          
        else
            return str;
    }
      
    // Driver Code
    public static void main(String args[])
    {
        // Given String str
        String str = "GeeksForGeeks";
          
        // Given a positive integer k
        int k = 5;
          
        // Print the first k characters
        // of the string
        System.out.println(
          firstKCharacters(str, k));
    }
}
Output
Geeks



Method 2: Without checking the size

  1. The idea is to use Math.min() function as an end index of the substring method.
  2. Find the minimum value between the length of the string and positive integer k.
  3. Get the substring from zero to the minimum of string length and k.
  4. Now, print the first k characters of the string.

Below is the implementation of the above approach:

Java




// Java program to print first k
// characters of the string
  
class GFG {
  
    // Function to print first k
    // characters of the string
    public static String firstKCharacters(String str, int k)
    {
        // Check if the string is
        // null or empty then
        // return null
        if (str == null || str.isEmpty())
            return null;
  
        // Return the first k characters
        // of the string if the string
        // length is less than k, otherwise
        // return the string as it is
        return str.substring(0, Math.min(str.length(), k));
    }
  
    // Driver Code
    public static void main(String args[])
    {
        // Given String str
        String str = "GeeksForGeeks";
  
        // Given a positive integer k
        int k = 5;
  
        // Print the first k characters
        // of the string
        System.out.println(firstKCharacters(str, k));
    }
}
Output
Geeks






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