1 MATERI PENDUKUNG TIPE DATA Matakuliah: M0074/PROGRAMMING II Tahun: 2005 Versi: 1/0

2 Data type Data types classify the kind of information that certain Java programming elements can contain. Data types fall into two main categories –Primitive or basic –Composite or reference Naturally, different kinds of data types can hold different kinds and amounts of information. You can convert the data type of a variable to a different type, within limits: you cannot cast to or from the boolean type, and you cannot cast an object to an object of an unrelated class. Java will prevent you from risking your data. This means it will easily let you convert a variable or object to a larger type, but will try to prevent you from converting it to a smaller type. When you change a data type with a larger capacity to one with a smaller capacity, you must use a type of statement called a type cast

3 Primitive data types Primitive, or basic, data types are classified as Boolean (specifying an on/off state), character (for single characters and Unicode characters), integer (for whole numbers), or floating-point (for decimal numbers). In code, primitive data types are all lower case. The Boolean data type is called boolean, and takes one of two values: true or false. Java doesn't store these values numerically, but uses the boolean data type to store these values. The character data type is called char and takes single Unicode characters with values up to 16 bits long. In Java, Unicode characters (letters, special characters, and punctuation marks) are put between single quotation marks: 'b'. Java's Unicode default value is \u0000, ranging from \u0000 to \uFFFF. Briefly, the Unicode numbering system takes numbers from 0 to 65535, but the numbers must be specified in hexadecimal notation, preceded by the escape sequence \u

4 Composite data types Each of the data types above accepts one number, one character, or one state. Composite, or reference, data types consist of more than a single element. Composite data types are of two kinds: classes and arrays. Class and array names start with an upper case letter and are camel-capitalized (that is, the first letter of each natural word is capitalized within the name, for instance, NameOfClass). A class is a complete and coherent piece of code that defines a logically unified set of objects and their behavior. For more information on classes, see Object-Oriented Programming in Java. Any class can be used as a data type once it has been created and imported into the program. Because the String class is the class most often used as a data type, we will focus on it in this chapter.