遍历一个对象并从其所有变量中获取值答案

【问题标题】：Loop through an object and get the value from all its variables遍历一个对象并从其所有变量中获取值
【发布时间】：2019-01-12 22:18:00
【问题描述】：

我正在使用 Gson 将 JSON 对象数组解析为 POJO。然后我使用for-loop 将每个解析的对象发送到一个方法进行处理。我似乎无法找到一种方法来遍历各个对象并获取其中包含的值。

例如：

private Double thing1;
private Double thing2;
private Dboule thing3;

private void doSomething(MyObject myObj){
 ...myObject contains thing1, thing2, thing3 which are each doubles.

//I want to loop through the entire object, 
//grab thing1's value and do something with it, then grab thing2's value... etc. 

 
}

这很容易做到吗？我已经尝试了一段时间，但我似乎无法让它发挥作用。我可以使用以下方法轻松地单独抓取它们：

myObj.thing1

但它需要在循环中完成，因为有大量的值进入。

更新：这几乎可以工作，但它会打印整个对象，然后打印单个对象值。我怎样才能让它只打印单个值而不先打印所有内容？

for(Field field : data.getClass().getDeclaredFields()){
    Object value = field.get(data);
    System.out.println(value);        
}

输出：

    [{"accel_1":0.012,"accel_2":0.125,"accel_3":0.03,"accel_4":0.012,"accel_5":0.125,"accel_6":0.03,"accel_7":0.012,"accel_8":0.125,"accel_9":0.03,"accel_10":0.012,"accel_11":0.125,"accel_12":0.03},{"accel_1":0.18,"accel_2":0.26,"accel_3":0.05,"accel_4":0.18,"accel_5":0.26,"accel_6":0.05,"accel_7":0.18,"accel_8":0.26,"accel_9":0.05,"accel_10":0.18,"accel_11":0.26,"accel_12":0.05},{"accel_1":0.06,"accel_2":0.02,"accel_3":0.03,"accel_4":0.06,"accel_5":0.02,"accel_6":0.03,"accel_7":0.06,"accel_8":0.02,"accel_9":0.03,"accel_10":0.06,"accel_11":0.02,"accel_12":0.03}]
0.012
0.125
0.03
0.012
0.125
0.03
0.012
0.125
0.03
0.012
0.125
0.03
[{"accel_1":0.012,"accel_2":0.125,"accel_3":0.03,"accel_4":0.012,"accel_5":0.125,"accel_6":0.03,"accel_7":0.012,"accel_8":0.125,"accel_9":0.03,"accel_10":0.012,"accel_11":0.125,"accel_12":0.03},{"accel_1":0.18,"accel_2":0.26,"accel_3":0.05,"accel_4":0.18,"accel_5":0.26,"accel_6":0.05,"accel_7":0.18,"accel_8":0.26,"accel_9":0.05,"accel_10":0.18,"accel_11":0.26,"accel_12":0.05},{"accel_1":0.06,"accel_2":0.02,"accel_3":0.03,"accel_4":0.06,"accel_5":0.02,"accel_6":0.03,"accel_7":0.06,"accel_8":0.02,"accel_9":0.03,"accel_10":0.06,"accel_11":0.02,"accel_12":0.03}]
0.18
0.26
0.05
0.18
0.26
0.05
0.18
0.26
0.05
0.18
0.26
0.05
[{"accel_1":0.012,"accel_2":0.125,"accel_3":0.03,"accel_4":0.012,"accel_5":0.125,"accel_6":0.03,"accel_7":0.012,"accel_8":0.125,"accel_9":0.03,"accel_10":0.012,"accel_11":0.125,"accel_12":0.03},{"accel_1":0.18,"accel_2":0.26,"accel_3":0.05,"accel_4":0.18,"accel_5":0.26,"accel_6":0.05,"accel_7":0.18,"accel_8":0.26,"accel_9":0.05,"accel_10":0.18,"accel_11":0.26,"accel_12":0.05},{"accel_1":0.06,"accel_2":0.02,"accel_3":0.03,"accel_4":0.06,"accel_5":0.02,"accel_6":0.03,"accel_7":0.06,"accel_8":0.02,"accel_9":0.03,"accel_10":0.06,"accel_11":0.02,"accel_12":0.03}]
0.06
0.02
0.03
0.06
0.02
0.03
0.06
0.02
0.03
0.06
0.02
0.03

这里是完整的方法：

private void convertJSON(String jsonString) throws IllegalArgumentException, IllegalAccessException {
    Gson gson = new Gson();
    Type data = new TypeToken<ArrayList<MyObject>>(){}.getType();
    List<MyObject> fhd = gson.fromJson(jsonString, data);
    for(MyObject current : fhd){
        printIt(current);
    }
}

public void printIt(MyObject data) throws IllegalArgumentException, IllegalAccessException{
    for(Field field : data.getClass().getDeclaredFields()){
        Object value = field.get(data);
        System.out.println(value);       
    }
}

【问题讨论】：

标签： java loops object

【解决方案1】：

您可以使用反射来做到这一点：

Field[] fields = games.getClass().getDeclaredFields();

for(Field field: fields) {
    //do stuff
}

getDeclaredFields():

返回一个 Field 对象数组，反映由该 Class 对象表示的类或接口声明的所有字段。这包括公共、受保护、默认（包）访问和私有字段，但不包括继承的字段。

【讨论】：

这几乎可以做到。我更新了我的帖子。快到了。
@MarcusHolden 你将什么传递给get() 方法？（data 是什么？）
它是一个取自对象数组的对象。这是模拟方法： public void printIt(MyObject data){ for(Field field : data.getClass().getDeclaredFields()){ Object value = field.get(data); System.out.println(值); } }
@MarcusHolden 嗯，我无法重现这个。当我运行此代码时，它只会打印出字段。
这太奇怪了。我已经上传了完整的方法。

【解决方案2】：

如果我对您的理解正确，您正在尝试遍历对象的值。如果是这种情况，请编写如下方法：

private void doSomething(MyObject myObj)
{
    Double sum_of_values = 0;
    for (MyObject val : myObj) // "val" will be each Double value within the object.
    { 
        //I don't know what you want to do with the values of your object,
        //but below is an example of getting the sum of values within your object:
        sum_of_values += val; 
        //here I assumed that are values are Double, which in many cases they can be of any type.
        //Or you can send each value to another method and do your stuff there:
        someMethod(val);
        //Or maybe do something else.
    }
}
private void someMethod(Double val)
{
    //do things here.
{

我希望这能给你一个想法

【讨论】：