引用自:https://www.cnblogs.com/dolphin0520/p/3920407.html
class DataFormatTest{
ThreadLocal<SimpleDateFormat> t = new ThreadLocal<SimpleDateFormat>();
public SimpleDateFormat getSimpleDateFormat(final String pattern){
if( t == null){
t = new ThreadLocal<SimpleDateFormat>(){
@Override
protected SimpleDateFormat initialValue() {
return new SimpleDateFormat(pattern);
}
};
}
return t.get();
}
}