当我运行代码时,它报告:
线程“主”中的异常java.lang.ClassCastException:
net.sf.json.JSONObject无法在...处强制转换为ColorData。
代码是:
public class JsonTest {
public static void main(String[] args) {
ArrayList<ColorData> list = new ArrayList<>();
ColorData data1 = new ColorData(1129, 0.35);
ColorData data2 = new ColorData(1120, 0.39);
list.add(data1);
list.add(data2);
Collections.sort(list);
// Java list to json
JSONArray jsonArray = (JSONArray) JSONSerializer.toJSON(list);
// json to Java
JSONArray jsonObject = JSONArray.fromObject(jsonArray);
ArrayList<ColorData> resList = new ArrayList<ColorData>();
for (int i = 0; i < jsonObject.size(); i++) {
ColorData data = (ColorData) jsonObject.get(i);
resList.add(data);
}
}
}
在将Java列表传递给Json之后,它的toString是:
[{"HSV":1120,"denominator":1,"numerator":1,"quantity":0.39},{"HSV":1129,"denominator":1,"numerator":1,"quantity":0.35}]
然后将此字符串读回到
jsonObject
,并将其解析为ColorData
,并将其存储在resList中。通过
jsonObject.get(i)
我可以获取每个数据,例如{"HSV":1120,"denominator":1,"numerator":1,"quantity":0.39}
,但是如何将其转换为ColorData实例呢?ColorData
类如下:public class ColorData implements Comparable<ColorData>{
private int HSV;
private double quantity;
private int numerator = 1;
private int denominator = 1;
// init the value
public ColorData (int HSV, double quantity) {
this.HSV = HSV;
this.quantity = quantity;
}
// getter and setter
public int getHSV() {
return HSV;
}
public void setHSV(int hSV) {
HSV = hSV;
}
public double getQuantity() {
return quantity;
}
public void setQuantity(double quantity) {
this.quantity = quantity;
}
public int getNumerator() {
return numerator;
}
public void setNumerator(int numerator) {
this.numerator = numerator;
}
public int getDenominator() {
return denominator;
}
public void setDenominator(int denominator) {
this.denominator = denominator;
}
@Override
public int compareTo(ColorData o) {
// TODO Auto-generated method stub
if (this.quantity - o.quantity > 0)
return -1;
else if (this.quantity - o.quantity < 0)
return 1;
else
return 0;
}
}
最佳答案
您需要一一读取属性并将其设置在数据对象中。
ColorData data;
for (int i = 0; i < jsonObject.size(); i++) {
data = new ColorData();
//{"HSV":1120,"denominator":1,"numerator":1,"quantity":0.39}
data.setHSV(((JSONObject)jsonObject.get(i)).getInt("HSV"));
data.setDenominator(((JSONObject)jsonObject.get(i)).getInt("denominator"));
data.setNumerator(((JSONObject)jsonObject.get(i)).getInt("numerator"));
data.setQuantity(((JSONObject)jsonObject.get(i)).getDouble("quantity"));
resList.add(data);
}
或者您可以使用GSON lib。