Short answer will be: no, it does not for public classes. But yes, it does for non-public ones.
According to JavaSE7 specification http://docs.oracle.com/javase/specs/jls/se7/html/jls-7.html#jls-7.6 it's up to compiler to allow or deny multiple public classes in one file:
If and only if packages are stored in a file system (§7.2), the host system may choose to enforce the restriction that it is a compile-time error if a type is not found in a file under a name composed of the type name plus an extension (such as .java or .jav) if either of the following is true:
In practise, all compilers I ever met applied this restriction. The rule is: one public class – one .java file (which is a compilation unit) with the same name.
For example, let's put two public classes in one file and we'll get compilation error:
* The public type SecondClass should be defined in it's own file
*/
package classesTest1;
public class OneClass {
}
public class SecondClass {
}
But if we place any number of non public classes in single file, the code will be compiled:
File: OneClass.java
*/
package classesTest1;
Public class should be placed in a file with the same name. But we can place non-public classes across any .java files:
File: OneClass.java
*/
package classesTest1;
File: Outer.java
package javaProject1;
/**
* Nested classes are Ok, no compilation errors produced
*/
class Outer {
public class Inner1 {
}
public class Inner2 {
}
public class Inner3 {
{
}
}
Some misunderstanding still exists in my mind. I understand that it's easier for compiler to find public class inside related compilation unit – .java file with the same name. But why it's not the same for non-public classes? It looks like some historical stuff from old Java.
