Knowledge Factory

In this section, we will show you how to convert a List<List<Object>> to a List<Object> in Java 8 using Stream API. Following ways can be used for converting  List<List<Object>> to a List<Object> :  1. By using flatMap () method  2. By using forEach () method 3. By using mapMult () method Example 1: Use flatMap () method Java 8 Stream flatMap () method is used to flatten a Stream of collections to a stream of objects. The objects are combined from all the collections in the original Stream. Flattening is referred to as merging multiple collections/arrays into one. import java.util.Arrays ; import java.util.Collections ; import java.util.List ; import java.util.stream.Collectors ; public class Main { // Driver code public static void main ( String [] args) { //Creating List of Lists List < List < String >> listOfLists = Collections . singletonList ( Arrays . asList ( &quo

In this section, we will show you how to generate random alphanumeric string of given size in Java. Example 1: Use SecureRandom import java.security.SecureRandom ; public class Main { //Create a String of the characters which can be included in the string private static final String ALPHA_NUMERIC_STRING = "ABCDEFGHIJKLMNOPQRSTUVWXY" + "Zabcdefghijklmnopqrstuvwxyz0123456789" ; // Driver code public static void main ( String [] args) { String randomAlphaNumericString = generateAlphaNumericString ( 25 ); System . out .println( randomAlphaNumericString ); } //Method to generate Random AlphaNumeric String public static String generateAlphaNumericString ( int length) { SecureRandom random = new SecureRandom(); StringBuilder builder = new StringBuilder(length); for ( int i = 0 ; i < length; i ++) { builder .append( ALPHA_NUMERIC_STRING .

In this section, we will show you how to convert a String to an int in Java.  Input : str = "3456"  Output : 3456 Input : str = "a3456e"  Output : 0 Input : str = "-3456"  Output : 3456 Following ways can be used for converting String to int: 1. By using Integer.parseInt() method 2. By using  NumberUtils.toInt method of Apache Commons library 3. By using  Ints::tryParse method of Guava library Example 1: Use Integer.parseInt() method Integer.parseInt() method parses the String argument as a signed decimal integer object. The characters in the string must be decimal digits, except that the first character of the string may be an ASCII minus sign '-' to indicate a negative value or an ASCII plus '+' sign to indicate a positive value. It returns the integer value which is represented by the argument in a decimal integer. public class Main { // Driver code public static void main ( String [] args) { //Example 1 S