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

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Introduction to Unit 5

The unit introduces two important Java programming concepts:

arrays
string objects ? instances of the String class

As with the previous unit, the concepts in this unit are not all explicitly about object-oriented programming. However, such concepts as arrays of objects, and objects of the String class illustrate how the concepts introduced in this unit are important for working with different kinds of non-primitive variable types, and also for the implementation of methods that process each member of an array.

The sequence of the topics in this unit is by design ?you will understand strings much easier if you have grasped the concepts of Java character arrays first.

Both of these concepts are related, since the words (and the spaces between them) below could be represented either as an array or an instance of the String class:

this is a sequence of characters

As you will discover working through this unit, we could declare an array of characters and initialise this array variable as follows:

char sentence = {'t', 'h', 'i', 's', ' ', 'i', 's', ... }

Or we could declare and initialise an instance of the String class to contain the sentence as follows:

String sentence = "this is a sequence of characters";

As can be seen above, arrays are designed around the individual values stored in them (i.e. each character is treated separately), while a String object stores and processes complete sequence of characters. However, String objects can only be used with characters, while arrays can be used to store organised collections of any type of value (character, objects, primitive types).

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