java - getResourceAsStream returns null randomly and infrequently -

i'm getting null pointer exception when using getresourceasstream once every 10000 runs. how class looks like

public class configloader{   private properties propies;   private static configloader cl = null;   private configloader(){         propies = new properties;   }   public static configloader getinstance(){     if(cl == null){           cl = new configloader();     }   }    public boolean load(){    try{          propies.load(this.getclass().getresourceasstream("/config.properties"));              }    catch(nullpointerexception e){          system.out.println("file not exist");          return false;    }    return true;    } } 

as can seen here, class implemented singleton. resource exists , detected of time i'm not sure why failing once in while seems strange me.

1. it find out null (propies? value returned getresourceasstream?)
2. my guess call getinstance several threads , 1 of them gets configloader has not been initialised because singleton not thread safe

so first confirm logging when fails, because propies null, , if case, make singleton thread safe, example:

private static final configloader cl = new configloader; public static configloader getinstance() { return cl; } 

or better use enum:

public enum configloader{   instance;   private properties propies;   private configloader(){     propies = new properties;   }    public static configloader getinstance(){ return instance; }    public boolean load(){    try{          propies.load(this.getclass().getresourceasstream("/config.properties"));              }    catch(nullpointerexception e){          system.out.println("file not exist");          return false;    }    return true;    } } 

alternatively, if getresourceasstream("/config.properties") returns null, packaging issue due resource not having been included in jar?