报错介绍 No enclosing instance of type B is accessible.

Java 报错 No enclosing instance of type B is accessible. Must qualify the allocation with an enclosin

在写 Java 并发的 Demo ，写的时候发现了一个报错： Java 出现 No enclosing instance of type TestB is accessible. Must qualify the allocation with an enclosing instance of type TestB(e.g. x.new A() where is an instance of TestB)
主要是我基础不好，这里通过网上查询发现了问题所在，这里就记录一下，先看代码：

public class TestB {
	public class ThreadA  {
	}

	public static void main(String[] args) {
		ThreadA teata = new ThreadA();
	}
}

public class TestB {
	 public static class ThreadA {		
	}
	public static void main(String[] args) {
		ThreadA teata = new ThreadA();
	}
}

public class TestB{
	public static void main(String[] args) {
		TestB teata = new TestB();
	}
}