,我在下面的代碼獲得NullPointerException異常:添加空單映射
private Map<String,List<Entry>> Days;
private void intializeDays() {
//Iterate over the DayOfWeek enum and put the keys in Map
for(DayOfWeek dw : EnumSet.range(DayOfWeek.MONDAY,DayOfWeek.SUNDAY)){
List<Entry> entries = null;
Days.put(dw.toString().toLowerCase(),entries);
}
}
我認爲它是因爲
List<Entry> entries = null;
但後來如何創建一個空的列表,並把它添加到地圖?
問題在於天映射。試試這個Days = new HashMap>(); –
Addict