Java programming ideology version 4 * Chapter 7 * personal exercises and programming ideology version 4

Java programming ideology version 4 * Chapter 7 * personal exercises and programming ideology version 4
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Exercise 1: (2) create a simple class. In the second class, a reference is defined as the object of the first class. Instantiate this object using inertia initialization.

Package test; public class Manager {public static void main (String args []) {Second s = new Second (); s. getFirst ();}/*** print the result: */} class First {} class Second {First f; Second () {System. out. println ("Creating Second");} First lazy () {if (f = null) {System. out. println ("Creating First"); f = new First ();} return f;} public First getFirst () {return lazy ();}}

Exercise 2: (2) inherit from Detergent to generate a new class. Override scrub () and add a new method named sterilize.

Package test; public class Manager {public static void main (String args []) {Sub s = new Sub (); s. apply (); s. dilute (); s. foam (); s. scrub (); s. sterilize (); new print (s);}/*** print the result: Cleanser apply () dilute () foam () sub. scrub Detergent. scrub () sub. sterilize () */} class print {print (Object obj) {System. out. println (obj) ;}} class Cleanser {private String s = "Cleanser"; public void append (String a) {s + = a;} public void dilute () {append ("dilute ()") ;}public void apply () {append ("apply ()") ;}public void scrub () {append ("scrub () ");} public String toString () {return s;} public static void main (String [] args) {Cleanser x = new Cleanser (); x. dilute (); x. apply (); x. scrub (); new print (x) ;}} class Detergent extends Cleanser {public void scrub () {append ("Detergent. scrub () ");} public void foam () {append (" foam () ");} class Sub extends Detergent {public void scrub () {append (" sub. scrub "); super. scrub ();} public void sterilize () {append ("sub. sterilize ()");}}

Exercise 3 (2) prove the previous two sentences (even if you do not create a constructor for Cartoon, the compiler will synthesize a default constructor for you, the constructor will call the constructor of the base class)

Package test; public class Manager {public static void main (String args []) {new Cartoon ();}/*** print the result: art constructor Drawing constructor */} class print {print (Object obj) {System. out. println (obj) ;}} class Art {Art () {new print ("Art constructor") ;}} class Drawing extends Art {Drawing () {new print ("Drawing constructor") ;}} class Cartoon extends Drawing {}

Exercise 4 (2) proves that the base class constructor is always called and called before exporting the class constructor.

Package test; public class Manager {public static void main (String args []) {new Child ();}/*** print the result: parent class constructor outputs subclass constructor outputs */} class print {print (Object obj) {System. out. println (obj) ;}} class Parent {Parent () {new print ("base class constructor output") ;}} class Child extends Parent {Child () {new print ("subclass constructor output ");}}

Exercise 5: (1) create two classes A and Class B with the default constructor (empty parameter list. Inherit from A to generate A new member named C and create A member of Class B in C. Do not write constructor for C. Create a class C object and observe its results.

Package test; public class Manager {public static void main (String args []) {new C ();}/*** print the result: ()...... B ()...... B ()...... C ()...... */} Class print {print (Object obj) {System. out. println (obj) ;}} class A {A () {new print ("()...... ") ;}} Class B {B () {new print (" B ()...... ") ;}} Class C extends A {private B B = new B (); C () {new print (" C ()...... ");} Private B b2 = new B ();}

Exercise 6: (1) Use Chess to prove the first two words

Package test; public class Manager {public static void main (String args []) {new Chess ();}/*** print the result: Exception in thread "main" java. lang. error: Unresolved compilation problem: Implicit super constructor BordGame () is undefined. must explicitly invoke another constructorat test. chess. <init> (Manager. java: 32) at test. manager. main (Manager. java: 6) */} class print {print (Object obj) {System. out. println (obj) ;}} class Game {Game (int I) {new print ("Game constructor") ;}} class BordGame extends Game {BordGame (int I) {super (I); new print ("BordGame constructor") ;}} class Chess extends BordGame {Chess () {// Implicit super constructor BordGame () is undefined. must explicitly invoke another constructornew print ("Chess constructor ");}}

Exercise 7: (1) Modify exercise 5 so that A and B Replace the default constructor with A constructor with parameters. Write a constructor for C and execute all initialization in it.

Package test; public class Manager {public static void main (String args []) {new C ();}/*** print the result: ()...... B ()...... B ()...... C ()...... */} Class print {print (Object obj) {System. out. println (obj) ;}} class A {A (int I) {new print ("()...... ") ;}} Class B {B () {new print (" B ()...... ") ;}} Class C extends A {private B B = new B (); C () {super (1); // new print (" C ()...... ");} Private B b2 = new B ();}

Exercise 8: (1) create a base class with only one non-default constructor, and create an export class with the default constructor and non-default constructor. Call the constructors of the base class in the constructor of the export class.

Package test; public class Test {public static void main (String [] args) {}} class A {/** non-default constructor **/A (int I) {System. out. println ("base class") ;}} class B extends A {B () {super (1 ); /** call the base class constructor **/} B (int I) {super (I);/** call the base class constructor **/System. out. println ("Export class ");}}

Exercise 9: (2) create a Root class that contains an instance of each class named Component1, Component 2, and Component3 (which is also written by you ). A Stem class derived from Root also contains the above "components ". All classes should have a default constructor that can print information about the class.

Package test; public class Test {public static void main (String [] args) {new Stem ();} /*** output Component1 component constructorRoot component constructorComponent3 constructorStem constructor */} class Root {private Component1 component1 = new Component1 (); private Component2 component2 = new Component2 (); private Component3 component3 = new Component3 (); Root () {System. out. println ("Root constructor") ;}} class Stem extends Root {private Component1 component1 = new Component1 (); private Component2 component2 = new Component2 (); private Component3 component3 = new Component3 (); Stem () {System. out. println ("Stem constructor") ;}} class Component1 {Component1 () {System. out. println ("Component1 constructor") ;}} class Component2 {Component2 () {System. out. println ("Component2 constructor") ;}} class Component3 {Component3 () {System. out. println ("Component3 constructor ");}}

Exercise 10: (1) Modify exercise 9 so that each class has only a non-default constructor.

Package test; public class Test {public static void main (String [] args) {new Stem (1 );} /*** output Component1 constructor 1Component2 constructor extends constructor 3 Root extends constructor 1Component2 constructor extends limit 3 Stem constructor */} class Root {private Component1 component1 = new Component1 (1 ); private Component2 component2 = new Component2 (2); private Component3 component3 = new Component3 (3); Root (int I) {System. out. println ("Root constructor") ;}} class Stem extends Root {private Component1 component1 = new Component1 (1); private Component2 component2 = new Component2 (2 ); private Component3 component3 = new Component3 (3); Stem (int I) {super (I); System. out. println ("Stem constructor") ;}} class Component1 {Component1 (int I) {System. out. println ("Component1 constructor" + I) ;}} class Component2 {Component2 (int I) {System. out. println ("Component2 constructor" + I) ;}} class Component3 {Component3 (int I) {System. out. println ("Component3 constructor" + I );}}

Exercise 11: (3) Modify Detergent. java. Use a proxy.

Package test; public class Test {public static void main (String args []) {Sub s = new Sub (); s. apply (); s. dilute (); s. foam (); s. scrub (); s. sterilize (); new print (s);}/*** print the result: Cleanser apply () dilute () foam () sub. scrub Detergent. scrub () sub. sterilize () */} class print {print (Object obj) {System. out. println (obj) ;}} class Cleanser {private String s = "Cleanser"; public void append (String a) {s + = a;} public void dilute () {append ("dilute ()") ;}public void apply () {append ("apply ()") ;}public void scrub () {append ("scrub () ");} public String toString () {return s;} public static void main (String [] args) {Cleanser x = new Cleanser (); x. dilute (); x. apply (); x. scrub (); new print (x) ;}} class Detergent {Cleanser = new Cleanser (); public void append (String str) {Cleanser. append (str);} public void dilute () {append ("dilute ()");} public void apply () {append ("apply ()");} public String toString () {return Cleanser. toString ();} public void scrub () {append ("Detergent. scrub () ");} public void foam () {append (" foam () ");} class Sub extends Detergent {public void scrub () {append (" sub. scrub "); super. scrub ();} public void sterilize () {append ("sub. sterilize ()");}}

Exercise 12: (3) Add the hierarchy of an appropriate dispose () method to all classes in exercise 9.

Package test; public class Test {public static void main (String [] args) {Stem s = new Stem (); try {s. toString ();} finally {s. dispose () ;}}/*** output Component1 constructorComponent2 constructorComponent3 constructorRoot implements multiple constructorStem disposeRoot dispose */} class Root {private Component1 component1 = new Component1 (); private Component2 component2 = new Component2 (); private Component3 component3 = new Component3 (); Root () {System. out. println ("Root constructor");} void dispose () {System. out. println ("Root dispose") ;}} class Stem extends Root {private Component1 component1 = new Component1 (); private Component2 component2 = new Component2 (); private Component3 component3 = new Component3 (); Stem () {System. out. println ("Stem constructor");} void dispose () {System. out. println ("Stem dispose"); super. dispose () ;}} class Component1 {Component1 () {System. out. println ("Component1 constructor");} void dispose () {System. out. println ("Component1 dispose") ;}} class Component2 {Component2 () {System. out. println ("Component2 constructor");} void dispose () {System. out. println ("Component2 dispose") ;}} class Component3 {Component3 () {System. out. println ("Component3 constructor");} void dispose () {System. out. println ("Component3 dispose ");}}

Exercise 13: (2) create a class with a method that is overloaded three times. Inherit to generate a new class and add a new overload definition for this method. This shows that these four methods can be used in the export class.

Package test; public class Test {public static void main (String [] args) {Stem s = new Stem (); s. a (); int I = 10; s. a (I); float f = 10f; s. a (f); double d = 10d; s. a (d);}/*** Output a () a (int) 10a (float) 10.0a (double) 10.0 */} class Root {void a () {System. out. println ("a ()");} void a (int I) {System. out. println ("a (int)" + I);} void a (float I) {System. out. println ("a (float)" + I) ;}} class Stem extends Root {void a (double I) {System. out. println ("a (double)" + I );}}

Exercise 14: (1) Add a service () to the Engine in Car. java and call this method in main.