使用toString（）从char []转换为String

Question

I have a char [].

StringBuffer x = new StringBuffer(name.toString());
StringBuffer y = new StringBuffer();
y.append(name);
String s1 = new String(name);

print x -> [C@42b3b079
print y -> metafactory
print s1 -> metafactory

Could you please tell me why the difference?

When I read the javadoc:

String java.lang.Object.toString()

Returns a string representation of the object. In general, the toString method 
returns    a string that "textually represents" this object. The result should be a   
concise but informative representation that is easy for a person to read. It is 
recommended that all subclasses override this method. 


The toString method for class Object returns a string consisting of the name of the   
class of which the object is an instance, the at-sign character `@', and the unsigned 
hexadecimal representation of the hash code of the object. In other words, this method 
returns a string equal to the value of:

                 getClass().getName() + '@' + Integer.toHexString(hashCode())

Looks like it depends on implementation. Shouldn't it be advisable to return a readable string instead with the toString() API.

Thanks

Answer 1

The code:

StringBuffer x = new StringBuffer(name.toString());

behaves the same as:

String name2str = name.toString(); //here the value of name2str is "[C@42b3b079"
StringBuffer x = new StringBuffer(name2str);

That's why print x -> [C@42b3b079 .

If you construct the StringBuffer as:

StringBuffer x = new StringBuffer(name);

Then print x -> metafactory .

The reason Object.toString() implemented like this is that, as the base of the inheritance chain, it really doesn't know what information of the subclasses should be added to the return value of toString() . So it just output the class name and the hashcode of the object, which can identify the instance, and it's readable in my opinion.

If you want to output every element of the array, just use the utility method java.util.Arrays.toString(name) .