结论：org.json.JSONObject的getString如果取不到对应的key会抛出异常,optString则不会
/**
* Returns the value mapped by {@code name} if it exists, coercing it if
* necessary, or throws if no such mapping exists.
*
* @throws JSONException if no such mapping exists.
*/
public String getString(String name) throws JSONException {
Object object = get(name);
String result = JSON.toString(object);
if (result == null) {
throw JSON.typeMismatch(name, object, "String");
}
return result;
} /**
* Returns the value mapped by {@code name} if it exists, coercing it if
* necessary, or the empty string if no such mapping exists.
*/
public String optString(String name) {
return optString(name, "");
}