java code writing pitfalls

java code writing pitfalls:

Common error:

Console error: Can not find or load the main class HelloWorld reasons: java.lang.NoClassDefFoundError: cn / itcast / day01 / demo01 / HelloWorld (wrong name: Helloworld)

Analysis: This is a novice common pitfalls: the package name or class name with the actual match.

E.g:

package cn.itcast.day01.demo01;

public class HelloWorld {
	public static void main(String[] args) {
		System.out.println("你好！");
		int[] b=new int[4];
		System.out.println(b[1]);
	}
}

　The above code is no problem, but if you folder (the package name) or file name (eg HelloWorld here) do not correspond, it will make such a mistake in running times.