I want to call a java method once in the background of a feature file, assign the value of the method to a variable and share it across scenarios

java class

public class Utilities {


    public static String generateRandomString(int length) {
        String chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        StringBuilder sb = new StringBuilder(length);
        for (int i = 0; i < length; i++) {
            int index = (int) (Math.random() * chars.length());
            sb.append(chars.charAt(index));
        }
        return sb.toString();
    }
}

Feature file

Background:
    * def RandomStringGenerator = Java.type('Utilities')
    * def randomString = callonce RandomStringGenerator.generateRandomString(10)
    * print 'a'+randomString

  Scenario: Use Random String
    * print 'b'+randomString

  Scenario: Use Random String in scenario2
    * print 'c'+randomString

The randomString is printing null instead of the string generated. i am using karate 0.9.5 version if that helps

Call the static Java method via JavaScript. You have missed to add package name of the java class Utilities. Replace the feature file like below.

Feature: call java static method

  Background: 
    * def generateData =
      """
      function(arg) {
      var JavaDemo = Java.type('com.tests.Utilities');
      
      return JavaDemo.generateRandomString(arg);  
      }
      """
    * def result = callonce generateData 10
    * print 'a'+result

  Scenario: Use same string value scenario1
    * print 'b'+result

  Scenario: Use same string value scenario2 
    * print 'c'+result

Official Karate Doc: https://github.com/karatelabs/karate#calling-java