public boolean isFull(){  //generally full
    	if(parcelIsFull() || hcparcelIsFull() || noSharingParcel())
    		return true;
    }

I want to know why i get this error

missing return statement

I have the value written as 'true' boolean as the returning value.

public boolean isFull(){ //generally full
if(parcelIsFull() || hcparcelIsFull() || noSharingParcel())
return true;
}

It's evaluating the line if(parcelIsFull() || hcparcelIsFull() || noSharingParcel()) .... if this is true, it returns true ..

but what happens if it evaluates to false?

You need

if( parcelIsFull() || hcparcelIsFull() || noSharingParcel() ) {
   return true;
} else {
  return false;
}

or just

public boolean isFull(){
  return ( parcelIsFull() || hcparcelIsFull() || noSharingParcel() );
}