public class BlankTest {
    public static void main(String[] args) {
        System.out.println(deleteMulBlank("hello yyo    koko  !!!"));
        System.out.println(deleteMulBlank("afsaf    fdsfdf   fsdfsdf fs fs dfsdfsfsdf sdfsdfsdf sdfsdf sd fs f sdf sdf sdfd"));
    }
    
    public static String deleteMulBlank(String str){
        return str.replaceAll("[ ]{2,}", " ");
    }
}