Hello every body I was using the JDK very well writing the code then i use "javac" to compile it then "java" to run it But Recently when i write a code and compile it then if i try to run it this exception appears to me "Exception in thread "main" java.lang.NoSuchMethodError " at first i thought there is something wrong in my code , i searched in the internet for a solving for this problem but i didn't find anything may help me Then i try to run the "HelloWorld" example i made it before, it runs i copied the code and pasted it in another file and changed the name to "HelloWorld2" and compile it by "javac" and tried to run it by "java" the same exception appears i was surprised why? it is the same code then i used the "javap" which decompile the code with both i found this difference in the first one (the old one) "public static void main(java.lang.String[])"; but in the second (the new one) "public static void main(String[])"; without java.lang then i compiled the old one which works and runs by "javac" and when i try to run it, it didn't run and give me the same exception i tried with some of my old codes it run and when i compile it by "javac" it doesn't work I searched to find a solution to this problem and i found nothing