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Java programming Exercises: Check whether a string contains only a certain set of characters (a-z, A-Z and 0-9)

Java Regular Expression: Exercise-1 with Solution

Write a Java program to check whether a string contains only a certain set of characters (in this case a-z, A-Z and 0-9).

Sample Solution:

Java Code:

import java.util.Scanner;
public class test {
 
   public static void main(String[] args) {
	   
	    System.out.println(validate("ABCDEFabcdef123450"));
		System.out.println(validate("SQL"));		
		System.out.println(validate("Java"));
		System.out.println(validate("*&%@#!}{"));
		System.out.println(validate("w3resource.com"));
        }

   public static boolean validate(String text) {
    return text.matches("^[\\w]+$");
  }
}

Sample Output: 

true
true
true
false
false

Pictorial Presentation:

Java Regular Expression: Check whether a string contains only a certain set of characters (a-z, A-Z and 0-9).
Java Regular Expression: Check whether a string contains only a certain set of characters (a-z, A-Z and 0-9).

Flowchart :

Flowchart: Check whether a string contains only a certain set of characters (a-z, A-Z and 0-9).

Java Code Editor:

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Java: Tips of the Day

What is the best way to filter a Java Collection?

Java 8 (2014) solves this problem using streams and lambdas in one line of code:

List<Person> beerDrinkers = persons.stream()
    .filter(p -> p.getAge() > 16).collect(Collectors.toList());

Use Collection#removeIf to modify the collection in place. (Notice: In this case, the predicate will remove objects who satisfy the predicate):

persons.removeIf(p -> p.getAge() <= 16);

lambdaj allows filtering collections without writing loops or inner classes:

List beerDrinkers = select(persons, having(on(Person.class).getAge(),
    greaterThan(16)));

Ref: https://bit.ly/3uwYid6