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

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Content Page # 19

Individual characters in String objects

String objects are not arrays, therefore we cannot use the square bracket notation to refer to or change a particular character in a String.

However, we can use the String class method charAt() which allows us to find out what character is at a particular position in a String object.

So although the String class is very versatile, what we cannot do is something like the following:

String text = "hello";
char x = text[1];

It appears to be a sensible way to assign the character variable x to be equal to the first character in the String variable text. However, it is not permissible because text is an object, not an array. We can, however, write

String text = "hello";
char x = text.charAt(1);

which has the effect we wanted to achieve.

Length of String objects

For the same reason, if "text" is a String object, we can't get its length by writing

int lengthOfString = text.length;

but we can write

int lengthOfString = text.length

This will return an integer value, which is the length of the String variable called "text".

The reason for this is that the class String provides a length() method, whereas .length is how we find out the length of an array.

Such differences between [1] and charAt(1), and length verses length() are things are often confusing when first encountered. However, as you progress in Java programming you will come to understand why these seemingly arbitrary distinctions occur.

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