How does a 'string' type string differ from a c-type string?

Answer 1

A char is a single character. A String is a collection of characters. It may be empty (zero characters), have one character, two character, or many characters - even a fairly long text.

The single quote (') is used to deliniate a character during assignment:

char someChar = 'a';

The double quote (") is used to delineate a string during assignment:

String someString = new String("hello there");

Note that char is a primitive data type in Java, while String is an Object. You CANNOT directly assign a char to a String (or vice versa). There is, however, a Character object that wraps the char primitive type, and Java allows method calls to be made on the char primitive (automagically converting the char to Character before doing so).

i.e. these ALL FAIL:

someString = SomeChar;

someString = new String(someChar);

However, these WILL work:

someString = Character.toString(someChar);

someString = someChar.toString();

Also note that a String is a static memory allocation, while a character's is dynamic. By that, I mean that when a String is created, it is allocated a memory location exactly big enough to fit the assigned string. Any change to that String forces and entirely new memory location to be allocated, the contents of the old String copied in (with the appropriate changes), and the old String object subject to garbage collection. Thus, making changes to a String object are quite inefficient (if you want that kind of behaviour, use StringBuffer instead).

A character is allocated but once; all subsequent changes to a character variable simply overwrite that same memory location, so frequent changes to a character variable incur no real penalty.

Answer 2

The 'string' (more correctly 'char') type in C and C++ is a single scalar variable that can hold one character in the host's character set. The c-type string is an array of 'char' types. In this context, the array is of fixed size, and you need to provide code to manipulate it.

In C++, you can have classes, and you can have a 'string' class, or type. In this context, you can have automatic allocation/deallocation, expansion/contraction, and manipulation provided by the class.

Answer 3

Strings "like this" are constant character-array literals, so they can be used as 'char *' or 'char []' values, but they cannot be modified.