Singleton Design Pattern in Java

• singleton is a way to restrict only one object per a class  

    There are multiple ways of creating a singleton object 

 1) eager initialized singleton 

      public class MySingelton1 {

private final static  MySingelton1 myobj =new MySingelton1();

private MySingelton1() {

System.out.println("new instance created MySingelton1");

}

public static MySingelton1 getMyobj() {

return myobj;

}

}

This class object is created  only once during the loading time itself 

2) lazy initialized singleton

  

   public class MySingelton2 {

private  static volatile MySingelton2 myobj=null;

private MySingelton2() {

System.out.println("new instance created MySingelton2");

}

public static MySingelton2 getMyobj() {

 if (myobj == null) {
synchronized (MySingelton2.class)
{
if (myobj == null) {
myobj = new MySingelton2();
}
}
}

return myobj;

}

}

 This class object is cretaed only once when you called the getMyobj() method for the first time.

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Convert from List to IN params for SQL

         Convert from List to IN params for SQL 


public static <T> String getWithINParam(List<T> paraList) {
try {
if (null != paraList)
return paraList.stream().map(s -> new                                                                                                      StringBuilder("'").append(s).append("'")).collect(joining(","));                                               
} catch (Exception e) {
LOG.error("Error in setting IN para for SQL  ", e);

}
return "''";
}

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