如果 java 中未指定修饰符会怎样?

What happens if a modifier is not specified in java?

 class BTNode
 {    
     BTNode left, right;
     int data;

     //constructors and methods
} 

这段代码中没有使用特定的修饰符。那么在修饰符的上下文中会发生什么?他们有什么默认行为吗?

来自 Java 文档:

If a class has no modifier (the default, also known as package-private), it is visible only within its own package (packages are named groups of related classes)

You can read about it here