?? airplane.java
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// reusing/Airplane.java
// TIJ4, Chapter Reusing, Exercise 1, page 241
/* Create a simple class. Inside a second class, define a reference to an object of
* the first class. Use lazy initialization to instantiate this object.
*/
import static org.greggordon.tools.Print.*;
class Engine {
private String s;
Engine() {
println("Engine()");
s = "Constructed";
}
public String toString() { return s; }
}
public class Airplane {
private String fuselage, wings, tail;
private Engine e;
public Airplane() {
println("Inside Airplane()");
fuselage = "Body";
wings = "Airfoils";
tail = "Empennage";
}
public String toString() {
if(e == null) // lazy (delayed) initialization:
e = new Engine();
return "fuselage = " + fuselage + ", " +
"wings = " + wings + ", " +
"tail = " + tail + ", " +
"Engine = " + e;
}
public static void main(String[] args) {
Airplane N1234 = new Airplane();
print(N1234);
}
}
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