I have seen some references refer to a access modifier in Java called private protected (both words together):
private protected someMethod() {
}
One of the pages I found referring to this is here. My school lesson also referred to this access modifier (and said it exists). Using it, however, results in an error in the Java language.
I tried with both variables and methods and I'm pretty sure it doesn't exist, but I want an explanation of what happened. Was it considered, then rejected? Or did it get removed in a newer version of Java?
Edit: I am not looking for info about the protected keyword.
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Removal of the access modifier
Java did originally have the private protected modifier, but it was removed in JDK 1.0.2 (the first stable version, the Java 1.0 we know today). A few tutorials regarding JDK 1.0.2 (here and here) say the following:
Note: The 1.0 release of the Java language supported five access levels: the four listed above plus
private protected. Theprivate protectedaccess level is not supported in versions of Java higher than 1.0; you should no longer be using it in your Java programs.
Another answer on SoftwareEngineering.SE states:
Java originally had such a modifier. It was written
private protectedbut removed in Java 1.0.
Now take a look at the Java Version History:
JDK 1.0
The first version was released on January 23, 1996 and called Oak. The first stable version, JDK 1.0.2, is called Java 1.
From this, we can conclude the tutorials regarding version 1.0.2 refer to the very first version, JDK 1.0, where the language was called Oak, but the one from SoftwareEngineering.SE refers to the first stable version, JDK 1.0.2 called Java 1.0, where it was removed.
Now if you try to search for it in the Java 1.0 documentation, you won't find it, because as mentioned earlier, it was removed in JDK 1.0.2, otherwise known as Java 1.0. This is proven again when you look at the "Last Modified" times for the link you posted. The link you posted was last modified in February of 1996. Java 1.0/JDK 1.0.2, when private protected was removed, was released after February of 1996, and according to the specification, August of 1996.
Reason for removal
Some sources also explain the reason for private protected, such as this one. To quote:
What was private protected?
Early on, the Java language allowed for certain combinations of modifiers, one of which was
private protected. The meaning ofprivate protectedwas to limit visibility strictly to subclasses (and remove package access). This was later deemed somewhat inconsistent and overly complex and is no longer supported.[5][5] The meaning of the
protectedmodifier changed in the Beta2 release of Java, and theprivate protectedcombination appeared at the same time. They patched some potential security holes, but confused many people.
And the SoftwareEngineering.SE also supports this, by saying that it wasn't worth the inconsistencies and extra complexity, so it was removed early on.
Interpretation
My interpretation of all this is that maybe, back in the Oak days, both were allowed to coexist (hence the combination). Since protected's meaning had changed1, there may have been a need for allowing private and protected at the same time. The introduction became too complex and wasn't worth it, and was thus dropped in the end. By the time Java 1.0/JDK 1.0.2 rolled around, it had been dropped and thus cannot be found in the documentation.
1ではOak言語仕様、セクション4.10、変数とメソッドへのアクセスデフォルトの修飾子は次のとおりであることに注意してくださいprotected。
デフォルトでは、クラス内のすべての変数とメソッドは保護された。
これは、現在のデフォルトのパッケージ アクセスとはまったく異なります。 は制限が厳しすぎ、緩すぎたprivate protectedため、が必要になる原因となった可能性があります。privateprotected