gaspersic/java-design-patterns
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

eliminate all warnings of checkstyle.

Browse Source
This commit is contained in:
zafarella 2015-09-24 13:29:39 -04:00
parent 36809537d9
commit 60f9b71278
6 changed files with 121 additions and 124 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

83
singleton/src/main/java/com/iluwatar/singleton/App.java
View File

@ -1,58 +1,63 @@
/** /**
* Singleton pattern. * Singleton pattern.
*/ */
package com.iluwatar.singleton; package com.iluwatar.singleton;
/** /**
*
* Singleton pattern ensures that the class ({@link IvoryTower}) can have only one * Singleton pattern ensures that the class ({@link IvoryTower}) can have only one
* existing instance per Java classloader instance and provides global access to it. * existing instance per Java classloader instance and provides global access to it.
* <p> * <p/>
* http://stackoverflow.com/questions/70689/what-is-an-efficient-way-to-implement-a-singleton-pattern-in-java * http://stackoverflow.com/questions/70689/what-is-an-efficient-way-to-implement-a-singleton-pattern-in-java
*<p> * <p/>
* The risk of this pattern is that bugs resulting from setting a singleton up in a distributed environment can * The risk of this pattern is that bugs resulting from setting a singleton up in
* be tricky to debug, since it will work fine if you debug with a single classloader. Additionally, these * a distributed environment can be tricky to debug, since it will work fine if you
* problems can crop up a while after the implementation of a singleton, since they may start out synchronous and * debug with a single classloader. Additionally, these problems can crop up a while
* only become async with time, so you it may not be clear why you are seeing certain changes in behaviour. * after the implementation of a singleton, since they may start out synchronous and
* <p> * only become async with time, so you it may not be clear why you are seeing certain
* changes in behaviour.
* <p/>
* http://stackoverflow.com/questions/17721263/singleton-across-jvm-or-application-instance-or-tomcat-instance * http://stackoverflow.com/questions/17721263/singleton-across-jvm-or-application-instance-or-tomcat-instance
*/ */
public class App { public class App {
/** /**
* Program entry point * Program entry point.
* @param args command line args *
*/ * @param args command line args
public static void main(String[] args) { */
public static void main(String[] args) {
// eagerly initialized singleton // eagerly initialized singleton
IvoryTower ivoryTower1 = IvoryTower.getInstance(); IvoryTower ivoryTower1 = IvoryTower.getInstance();
IvoryTower ivoryTower2 = IvoryTower.getInstance(); IvoryTower ivoryTower2 = IvoryTower.getInstance();
System.out.println("ivoryTower1=" + ivoryTower1); System.out.println("ivoryTower1=" + ivoryTower1);
System.out.println("ivoryTower2=" + ivoryTower2); System.out.println("ivoryTower2=" + ivoryTower2);
// lazily initialized singleton // lazily initialized singleton
ThreadSafeLazyLoadedIvoryTower threadSafeIvoryTower1 = ThreadSafeLazyLoadedIvoryTower ThreadSafeLazyLoadedIvoryTower threadSafeIvoryTower1 = ThreadSafeLazyLoadedIvoryTower
.getInstance(); .getInstance();
ThreadSafeLazyLoadedIvoryTower threadSafeIvoryTower2 = ThreadSafeLazyLoadedIvoryTower ThreadSafeLazyLoadedIvoryTower threadSafeIvoryTower2 = ThreadSafeLazyLoadedIvoryTower
.getInstance(); .getInstance();
System.out.println("threadSafeIvoryTower1=" + threadSafeIvoryTower1); System.out.println("threadSafeIvoryTower1=" + threadSafeIvoryTower1);
System.out.println("threadSafeIvoryTower2=" + threadSafeIvoryTower2); System.out.println("threadSafeIvoryTower2=" + threadSafeIvoryTower2);
// enum singleton // enum singleton
EnumIvoryTower enumIvoryTower1 = EnumIvoryTower.INSTANCE; EnumIvoryTower enumIvoryTower1 = EnumIvoryTower.INSTANCE;
EnumIvoryTower enumIvoryTower2 = EnumIvoryTower.INSTANCE; EnumIvoryTower enumIvoryTower2 = EnumIvoryTower.INSTANCE;
System.out.println("enumIvoryTower1=" + enumIvoryTower1); System.out.println("enumIvoryTower1=" + enumIvoryTower1);
System.out.println("enumIvoryTower2=" + enumIvoryTower2); System.out.println("enumIvoryTower2=" + enumIvoryTower2);
InitializingOnDemandHolderIdiom demandHolderIdiom = InitializingOnDemandHolderIdiom.getInstance(); InitializingOnDemandHolderIdiom demandHolderIdiom =
System.out.println(demandHolderIdiom); InitializingOnDemandHolderIdiom.getInstance();
InitializingOnDemandHolderIdiom demandHolderIdiom2 = InitializingOnDemandHolderIdiom.getInstance(); System.out.println(demandHolderIdiom);
System.out.println(demandHolderIdiom2); InitializingOnDemandHolderIdiom demandHolderIdiom2 =
InitializingOnDemandHolderIdiom.getInstance();
System.out.println(demandHolderIdiom2);
ThreadSafeDoubleCheckLocking dcl1 = ThreadSafeDoubleCheckLocking.getInstance(); ThreadSafeDoubleCheckLocking dcl1 = ThreadSafeDoubleCheckLocking.getInstance();
System.out.println(dcl1); System.out.println(dcl1);
ThreadSafeDoubleCheckLocking dcl2 = ThreadSafeDoubleCheckLocking.getInstance(); ThreadSafeDoubleCheckLocking dcl2 = ThreadSafeDoubleCheckLocking.getInstance();
System.out.println(dcl2); System.out.println(dcl2);
} }
} }

15
singleton/src/main/java/com/iluwatar/singleton/EnumIvoryTower.java
View File

@ -1,18 +1,15 @@
/**
* Enum Singleton class.
* Effective Java 2nd Edition (Joshua Bloch) p. 18
*/
package com.iluwatar.singleton; package com.iluwatar.singleton;
/** /**
* Enum based singleton implementation. * Enum based singleton implementation.
* Effective Java 2nd Edition (Joshua Bloch) p. 18
*/ */
public enum EnumIvoryTower { public enum EnumIvoryTower {
INSTANCE; INSTANCE;
@Override @Override
public String toString() { public String toString() {
return getDeclaringClass().getCanonicalName() + "@" + hashCode(); return getDeclaringClass().getCanonicalName() + "@" + hashCode();
} }
} }

28
singleton/src/main/java/com/iluwatar/singleton/InitializingOnDemandHolderIdiom.java
View File

@ -1,6 +1,3 @@
/**
* Singleton pattern.
*/
package com.iluwatar.singleton; package com.iluwatar.singleton;
import java.io.Serializable; import java.io.Serializable;
@ -18,21 +15,22 @@ import java.io.Serializable;
*/ */
public class InitializingOnDemandHolderIdiom implements Serializable { public class InitializingOnDemandHolderIdiom implements Serializable {
private static final long serialVersionUID = 1L; private static final long serialVersionUID = 1L;
private InitializingOnDemandHolderIdiom() { private InitializingOnDemandHolderIdiom() {
} }
public static InitializingOnDemandHolderIdiom getInstance() { public static InitializingOnDemandHolderIdiom getInstance() {
return HelperHolder.INSTANCE; return HelperHolder.INSTANCE;
} }
protected Object readResolve() { protected Object readResolve() {
return getInstance(); return getInstance();
} }
private static class HelperHolder { private static class HelperHolder {
public static final InitializingOnDemandHolderIdiom INSTANCE = new InitializingOnDemandHolderIdiom(); public static final InitializingOnDemandHolderIdiom INSTANCE =
} new InitializingOnDemandHolderIdiom();
}
} }

39
singleton/src/main/java/com/iluwatar/singleton/IvoryTower.java
View File

@ -1,6 +1,3 @@
/**
* Singleton pattern.
*/
package com.iluwatar.singleton; package com.iluwatar.singleton;
/** /**
@ -10,24 +7,24 @@ package com.iluwatar.singleton;
*/ */
public final class IvoryTower { public final class IvoryTower {
/** /**
* Static to class instance of the class. * Static to class instance of the class.
*/ */
private static IvoryTower instance = new IvoryTower(); private static IvoryTower instance = new IvoryTower();
/** /**
* Private constructor so nobody can instantiate the class. * Private constructor so nobody can instantiate the class.
*/ */
private IvoryTower() { private IvoryTower() {
} }
/** /**
* To be called by user to * To be called by user to
* obtain instance of the class. * obtain instance of the class.
* *
* @return instance of the singleton. * @return instance of the singleton.
*/ */
public static IvoryTower getInstance() { public static IvoryTower getInstance() {
return instance; return instance;
} }
} }

48
singleton/src/main/java/com/iluwatar/singleton/ThreadSafeDoubleCheckLocking.java
View File

@ -1,7 +1,3 @@
/**
* Singleton pattern.
*
*/
package com.iluwatar.singleton; package com.iluwatar.singleton;
/** /**
@ -15,29 +11,35 @@ package com.iluwatar.singleton;
*/ */
public class ThreadSafeDoubleCheckLocking { public class ThreadSafeDoubleCheckLocking {
private static volatile ThreadSafeDoubleCheckLocking INSTANCE; private static volatile ThreadSafeDoubleCheckLocking INSTANCE;
/** /**
* private constructor to prevent client from instantiating. * private constructor to prevent client from instantiating.
*/ */
private ThreadSafeDoubleCheckLocking() { private ThreadSafeDoubleCheckLocking() {
//to prevent instantiating by Reflection call //to prevent instantiating by Reflection call
if (INSTANCE != null) if (INSTANCE != null) {
throw new IllegalStateException("Already initialized."); throw new IllegalStateException("Already initialized.");
} }
}
public static ThreadSafeDoubleCheckLocking getInstance() { /**
//local variable increases performance by 25 percent * Public accessor.
//Joshua Bloch "Effective Java, Second Edition", p. 283-284 *
ThreadSafeDoubleCheckLocking result = INSTANCE; * @return an instance of the class.
*/
public static ThreadSafeDoubleCheckLocking getInstance() {
//local variable increases performance by 25 percent
//Joshua Bloch "Effective Java, Second Edition", p. 283-284
ThreadSafeDoubleCheckLocking result = INSTANCE;
if (result == null) {
synchronized (ThreadSafeDoubleCheckLocking.class) {
result = INSTANCE;
if (result == null) { if (result == null) {
synchronized (ThreadSafeDoubleCheckLocking.class) { INSTANCE = result = new ThreadSafeDoubleCheckLocking();
result = INSTANCE;
if (result == null) {
INSTANCE = result = new ThreadSafeDoubleCheckLocking();
}
}
} }
return result; }
} }
return result;
}
} }

30
singleton/src/main/java/com/iluwatar/singleton/ThreadSafeLazyLoadedIvoryTower.java
View File

@ -1,6 +1,3 @@
/**
* Singleton pattern.
*/
package com.iluwatar.singleton; package com.iluwatar.singleton;
/** /**
@ -10,20 +7,21 @@ package com.iluwatar.singleton;
*/ */
public class ThreadSafeLazyLoadedIvoryTower { public class ThreadSafeLazyLoadedIvoryTower {
private static ThreadSafeLazyLoadedIvoryTower instance = null; private static ThreadSafeLazyLoadedIvoryTower instance = null;
private ThreadSafeLazyLoadedIvoryTower() { private ThreadSafeLazyLoadedIvoryTower() {
}
/**
* The instance gets created only when it is called for first time.
* Lazy-loading
*/
public synchronized static ThreadSafeLazyLoadedIvoryTower getInstance() {
if (instance == null) {
instance = new ThreadSafeLazyLoadedIvoryTower();
} }
public synchronized static ThreadSafeLazyLoadedIvoryTower getInstance() { return instance;
/* }
* The instance gets created only when it is called for first time.
* Lazy-loading
*/
if (instance == null) {
instance = new ThreadSafeLazyLoadedIvoryTower();
}
return instance;
}
} }