Java 天地·Core Java·Lecture Notes·Unitt5 - Array and Strings

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Content Page # 17

Motivation for String class

As you may have found in the first part of this unit, arrays of characters can be a little fiddly to deal with, since each character element has to be dealt with individually.

The text "hello" could be seen as a kind of array. It has 5 elements. Element 0 is the character "h", element 1 is the "e" and so on. This can be written in Java like this:

char text[] = {'h','e','l','l','o'};

After this line, the array "text" will contain the five characters that make up the word "hello". We can read the individual array elements in just the same way as any other array, e.g.,

char myChar = text[4];

This will make the character variable called "myChar" contain the character "o".

However, this is not a very useful way of manipulating text except when we need to process individual characters. Normally we would use a String object to work with such text.

The String class, provided as 'built-in' by the developers of the Java language, makes working with sequences of characters much easier. The String class defines methods for many actions, including:

finding the length of a string
locating a character or sub-string within a string
concatenating two strings together to create a new String object
converting primitive types to Strings
comparing the values inside String objects

Since many tasks where people interact with computers involves working with text on screen (word processors, databases, document viewing on the internet etc.) providing a class to make working with sequences of characters makes a lot of sense.

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