Java™ Application Development on Linux - Dator

58Chapter 3An Experienced Programmer’s Introduction to Javaaddresses, and so on. Java is an object-oriented programming language and thushas some significant syntax related to OO concepts.If you are new to object-oriented programming, be sure to read Chapter 1of Eckel’s Thinking in Java.In Java, we define a class to represent the objects about which we want toprogram. A class consists of the data and the methods to operate on that data.When we create a new instance of some class, that instance is an object of thattype of class. Example 3.5 shows a simple class.Example 3.5 Simple classclassPairInt{// dataint i;int j;}// constructorsPairInt() { i=0; j=0; }PairInt(int ival, int jval) { i=ival; j=jval; }// methodssetI(int val) { i=val; }setJ(int val) { j=val; }int getI() { return i; }int getJ() { return j; }Note that this class defines both data (i, j) and methods (setI(),getJ(), and so on). We put all this into a file named PairInt.java to matchthe name of the class definition.If some other Java code wanted to create and use a PairInt object, itwould create it with the new keyword followed by a call to a constructor(Example 3.6).This example shows only a snippet of code, not the entire PairInt class.That class, though, would likely reside in its own source file (named for its classname). In Java you normally create lots of files, one for each class. When it’s