Why is Java “String” type written in capital lette

问题:

I am curious. Why do I have to type String myStr with a capital letter whereas I type int aNumba with a lower-case letter?

回答1:

Because int is a primitive type, not a class, thus it is not directly comparable to String. The corresponding class type is Integer, spelled according to the class naming conventions.

Similar pairs of primitive and class types are

• byte vs Byte
• short vs Short
• long vs Long
• float vs Float
• double vs Double
• boolean vs Boolean
• char vs Character

回答2:

String itself is a class derived from Object, while int is a primitive.

Your confusion probably comes from the fact that String behaves in many ways like a primitive, in such that it has basic operations that can be applied to it, like the (+) concatenation, and that it does not need to be imported.

The concatenation is because it is fundamental enough to have this added operation applied, even though it is an object type.

The reason it does not need to be imported, is by default the java.lang package is imported, of which String is member.

回答3:

I'll join the party too: It's all convention.

And thank-goodness:

class billybobstype {
    ...
}

(It's all convention. There is no reason why "String" couldn't have been "string"; however, "int" is a keyword and more than just a classname -- of which CamelCase is the convention but not a requirement -- so it would require a compiler modification :-)

Edit: As an aside, C# has the 'string' keyword (part of the language grammar) which is an alias for the 'System.String' class. (C# also implements 'int', 'long', etc. as aliases this way, but it can do this because it has an extensible "value type" system whereas the the JVM only considers/allows-for a small discreet set of "value types".)

回答4:

int is a primitive data type, String derives from Object and is a class.

回答5:

Because String is a class (ie an object) and int is not

see Java naming conventions for more infos.

回答6:

because int is a primitive type whereas String is an object type

回答7:

By convention, java Objects have capitalized first-letter names (e.g. String), while primitives have lower case names (e.g. int, float, double, etc.)

回答8:

Basic low-level types like byte or integer are named in lowercase, and high-level objects/classes are named uppercase (CamelCase). That's just the way Java was designed.

回答9:

It's just something that original Java designers imposed on us :-)

回答10:

I can't believe some of the answers to this question!! The answer does not pertain to convention, and if you think that's the answer you need to do some more studying. int is a primitive type whereas String is a class (see Peter's answer).

An important caveat of primitive versus complex is autoboxing:

http://download.oracle.com/javase/1.5.0/docs/guide/language/autoboxing.html

Here's the Java tutorial for primitives:

http://download.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

The string class is a special case as well:

http://www.javabeginner.com/learn-java/java-string-class

Read up people!