Typical double check

DoubleCheck.java

class DoubleCheck {
  private SomeResource myResource;

  public SomeResource getResource() {
    if(myResource != null) {
      return myResource
    }
    synchronized(this) {
      if(myResource != null) {
        return myResource
      }
      myResource = new SomeResource();
      return myResource
    }
  }
}