java replace all spaces with underscore in string

/**
 * @author lautturi.com 
 * Java example: Java replace all spaces with underscore in string
 */

import java.util.*;

public class Lautturi {
	public static void main(String[] args) {

		String str = "welcom to java world. java is a high-level programming language.";
		
		str = str.replaceAll(" ", "_");
		// replace all white spaces(ordinary space,a tab, new line etc. )
		// str = str.replaceAll("\\s+", "_"); 
				
		System.out.println(str);
	}
}

output:

welcom_to_java_world._java_is_a_high-level_programming_language.