Java 为什么break不结束while循环?
我有一些建议:Java 为什么break不结束while循环?,java,json,Java,Json,我有一些建议: {"continue":{"continue":"||","rvcontinue":"20021126020855|1194424"},"query":{"pages":{"468997":{"ns":0,"revisions":[{"revid":445765,"comment":"","user":"Nate Silva","parentid":0,"timestamp":"2002-11-26T02:01:24Z"}],"pageid":468997,"title":"Vo
{"continue":{"continue":"||","rvcontinue":"20021126020855|1194424"},"query":{"pages":{"468997":{"ns":0,"revisions":[{"revid":445765,"comment":"","user":"Nate Silva","parentid":0,"timestamp":"2002-11-26T02:01:24Z"}],"pageid":468997,"title":"Vodafone"}}}}
我想递归地解析json中的时间戳:
private static LocalDate getTimeStamp(JSONObject json) throws IOException {
Iterator<?> keys = json.keys();
LocalDate ld = null;
// iterate recursively over all keys from the JSON until current key is
// timestamp
while (keys.hasNext()) {
String key = (String) keys.next();
if (key.equals("timestamp")) {
// timezone does not matter, as we just want to extract the date
DateTimeFormatter formatter = DateTimeFormatter.ofPattern(
"yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ENGLISH);
ld = LocalDate.parse(json.get(key).toString(), formatter);
System.out.println(ld);
break;
}
// if the current value is another JSON object, call setTimeStamp
// with value as param
else if (json.get(key) instanceof JSONObject) {
getTimeStamp((JSONObject) json.get(key));
}
// handle current value being JSON array
else if (json.get(key) instanceof JSONArray) {
JSONArray jarray = (JSONArray) json.get(key);
for (int i = 0; i < jarray.length(); i++) {
if (jarray.get(i) instanceof JSONObject) {
getTimeStamp((JSONObject) jarray.get(i));
}
}
}
}
System.out.println(ld);
return ld;
}
private static LocalDate getTimeStamp(JSONObject json)抛出IOException{
迭代器keys=json.keys();
LocalDate ld=null;
//递归迭代JSON中的所有键,直到当前键
//时间戳
while(keys.hasNext()){
字符串键=(字符串)键。下一步();
if(key.equals(“时间戳”)){
//时区不重要,因为我们只想提取日期
DateTimeFormatter formatter=DateTimeFormatter.of模式(
“yyyy-MM-dd'T'HH:MM:ss'Z'”,Locale.ENGLISH);
ld=LocalDate.parse(json.get(key.toString(),格式化程序);
系统输出打印项次(ld);
打破
}
//如果当前值是另一个JSON对象,则调用setTimeStamp
//以值作为参数
else if(json.get(key)JSONObject实例){
getTimeStamp((JSONObject)json.get(key));
}
//处理当前值为JSON数组
else if(json.get(key)instanceof JSONArray){
JSONArray jarray=(JSONArray)json.get(key);
for(int i=0;i
我试着调试它,但我不明白为什么在调用break
后调用该方法。它返回null而不是时间戳,尽管它到达了代码的这一部分。键嵌套在JSON中,因此需要对方法进行一些递归调用才能到达它
进行递归调用时,应使用这些调用返回的值
改变
getTimeStamp((JSONObject) json.get(key));
到
改变
getTimeStamp((JSONObject) jarray.get(i));
到
您的代码返回
null
,因为您忽略了递归调用的结果。您应该将它们存储在变量中,如果它不是null
,则返回它:
while (keys.hasNext() && ld == null) {
...
else if (json.get(key) instanceof JSONObject) {
ld = getTimeStamp((JSONObject) json.get(key));
}
// handle current value being JSON array
else if (json.get(key) instanceof JSONArray) {
JSONArray jarray = (JSONArray) json.get(key);
for (int i = 0; i < jarray.length(); i++) {
if (jarray.get(i) instanceof JSONObject) {
ld = getTimeStamp((JSONObject) jarray.get(i));
if (ld != null)
break;
}
}
}
}
while(keys.hasNext()&&ld==null){
...
else if(json.get(key)JSONObject实例){
ld=getTimeStamp((JSONObject)json.get(key));
}
//处理当前值为JSON数组
else if(json.get(key)instanceof JSONArray){
JSONArray jarray=(JSONArray)json.get(key);
for(int i=0;i
请注意,由于您正在查找第一个时间戳,
while
循环应在ld
变为非null
调用break
后调用什么方法时停止。程序正在递归工作。我怀疑类似于。它返回null
,因为“continue”
不等于“timestamp”
(并且忽略递归调用的结果)。如果不中断,可能意味着“if(key.equals(“timestamp”){”不工作。key不等于timestamp?
ld = getTimeStamp((JSONObject) jarray.get(i));
if (ld != null) return ld;
while (keys.hasNext() && ld == null) {
...
else if (json.get(key) instanceof JSONObject) {
ld = getTimeStamp((JSONObject) json.get(key));
}
// handle current value being JSON array
else if (json.get(key) instanceof JSONArray) {
JSONArray jarray = (JSONArray) json.get(key);
for (int i = 0; i < jarray.length(); i++) {
if (jarray.get(i) instanceof JSONObject) {
ld = getTimeStamp((JSONObject) jarray.get(i));
if (ld != null)
break;
}
}
}
}