java 怎樣 改變 數組元素的值

• 2020 年 7 月 8 日
• 筆記
• 實戰問題集錦

• 簡介 （Introduction）：

  •  背景 需要解析Object數組中的數據,將數據(mintime)進行修改,改為(maxtime),修改後,生成新的對象

  • 結構圖

  •  核心 對於Object數組的概念理解,對於數組的解析理解,數組賦值的理解 詳見://www.cnblogs.com/liuyangfirst/p/12364850.html

  •  快速上手（Getting Started）

測試數據

1、創建測試對象

 1 class FunctionType {
 2 
 3 
 4     private String functionType;
 5 
 6     private Object[] objects;
 7 
 8 
 9     private boolean isDistinct;
10 
11 
12     public String getFunctionType() {
13         return functionType;
14     }
15 
16     public void setFunctionType(String functionType) {
17         this.functionType = functionType;
18     }
19 
20     public Object[] getObjects() {
21         return objects;
22     }
23 
24     public void setObjects(Object[] objects) {
25         this.objects = objects;
26     }
27 
28     public boolean isDistinct() {
29         return isDistinct;
30     }
31 
32     public void setDistinct(boolean distinct) {
33         isDistinct = distinct;
34     }
35 
36     @Override
37     protected Object clone() {
38 
39         FunctionType functionTypeDemo = new FunctionType();
40 
41         if (objects != null) {
42             functionTypeDemo.setObjects(objects.clone());
43         }
44 
45         functionTypeDemo.setFunctionType(functionType);
46 
47         functionTypeDemo.setDistinct(isDistinct);
48 
49         return functionTypeDemo;
50     }
51 }

View Code

2、創建測試數據

 1         FunctionType functionType = new FunctionType();
 2 
 3         functionType.setDistinct(false);
 4         functionType.setFunctionType("max");
 5         Object[] objects2 = new Object[1];
 6         objects2[0] = "mintime";
 7         functionType.setObjects(objects2);
 8 
 9         FunctionType functionType2 = new FunctionType();
10 
11         functionType2.setFunctionType("from_unixtime");
12         functionType2.setDistinct(false);
13         Object[] objects3 = new Object[2];
14         objects3[0] = functionType;
15         objects3[1] = "yyyy-MM-dd HH24:mi:ss";
16 
17         functionType2.setObjects(objects3);

View Code

3、創建修改方法

 1  private static void changeObjectParam(FunctionType functionType2, String string) {
 2         Object[] objects = functionType2.getObjects();
 3 
 4 
 5         // 替換
 6         Object[] replace = new Object[1];
 7         replace[0] = new String(string);
 8 
 9         for (int i = 0; i < objects.length; i++) {
10             if (objects[0] instanceof FunctionType) {
11                 FunctionType o = (FunctionType) objects[0];
12                 if("max".equalsIgnoreCase(o.getFunctionType())){
13                     if("mintime".equalsIgnoreCase(o.getObjects()[0].toString())){
14                         o.setObjects(replace);
15                     }
16                 }
17 
18 
19                 break;
20             }
21         }
22 
23 
24         System.out.println(new Gson().toJson(functionType2));
25     }

View Code

4、測試

 1 public static void main(String[] args) {
 2         
 3 
 4         FunctionType functionType = new FunctionType();
 5 
 6         functionType.setDistinct(false);
 7         functionType.setFunctionType("max");
 8         Object[] objects2 = new Object[1];
 9         objects2[0] = "mintime";
10         functionType.setObjects(objects2);
11 
12         FunctionType functionType2 = new FunctionType();
13 
14         functionType2.setFunctionType("from_unixtime");
15         functionType2.setDistinct(false);
16         Object[] objects3 = new Object[2];
17         objects3[0] = functionType;
18         objects3[1] = "yyyy-MM-dd HH24:mi:ss";
19 
20         functionType2.setObjects(objects3);
21 
22         String string ="replace";
23 
24         // 修改mintime為maxtime
25         // 修改mintime為maxtime
26         changeObjectParam(functionType2, string);
27 
28 
29     }

View Code

•  環境 JDK1.8

  •  配置 IDEA編輯

  •  存在問題 暫無

  •  進階篇 （Advanced）：
    拓展object[]數據操作方法
    1、根據傳入的key，獲取object中存的值
    (1)方法

    

     1 /**
     2      * 獲取object中存的值
     3      *
     4      * @param obj 傳入的Object
     5      * @param key 傳入的字段名稱
     6      * @return 獲取object中存的值
     7      */
     8     public static String getValueByKey(Object obj, String key) {
     9 
    10         // 得到類對象
    11         Class<?> objClass = obj.getClass();
    12         // 得到類中的所有屬性集合
    13         Field[] fs = objClass.getDeclaredFields();
    14 
    15         for (Field f : fs) {
    16 
    17             // 設置些屬性是可以訪問的
    18             f.setAccessible(true);
    19 
    20             try {
    21 
    22                 if (f.getName().endsWith(key)) {
    23                     return f.get(obj).toString();
    24                 }
    25 
    26             } catch (IllegalArgumentException | IllegalAccessException e) {
    27                 e.printStackTrace();
    28             }
    29         }
    30 
    31         return "";
    32     }

    View Code

    (2)測試

    

     1 public static void main(String[] args) {
     2 
     3         Object[] objects = new Object[5];
     4         UserVO userVO = new UserVO("zhansan", "888");
     5         objects[0] = userVO;
     6         objects[1] = new Date();
     7         // name 是UserVO對象的字段屬性名
     8         String name = getValueByKey(objects[0], "name");
     9         System.out.println("value: " + name);
    10 }

    View Code

    2、根據傳入的值，獲取object中存的key

    (1)方法

    

     1 /**
     2      * 獲取object中存的關鍵字
     3      *
     4      * @param obj 傳入的Object
     5      * @return 獲取object中存的關鍵字
     6      */
     7     public static String getKey(Object obj) {
     8 
     9         // 得到類對象
    10         Class<?> objClass = obj.getClass();
    11         // 得到類中的所有屬性集合
    12         Field[] fs = objClass.getDeclaredFields();
    13 
    14         for (Field f : fs) {
    15 
    16             // 設置些屬性是可以訪問的
    17             f.setAccessible(true);
    18 
    19             try {
    20 
    21                 return f.getName();
    22 
    23             } catch (IllegalArgumentException e) {
    24                 e.printStackTrace();
    25             }
    26         }
    27 
    28         return "";
    29     }

    View Code

    (2)測試

    

     1 public static void main(String[] args) {
     2 
     3         Object[] objects = new Object[5];
     4         UserVO userVO = new UserVO("zhansan", "888");
     5         objects[0] = userVO;
     6         objects[1] = new Date();
     7 
     8         String key = getKey(objects[0]);
     9         System.out.println("key: " + key);
    10 }

    View Code

    3、根據傳入的key，修改object[]中的對象的值

    (1)方法

    

     1 /**
     2      * 修改object中參數的值
     3      *
     4      * @param obj      傳入的Object
     5      * @param key      傳入的字段名稱
     6      * @param newValue 改變的值
     7      */
     8     public static void changeObjectValueByKey(Object obj, String key, String newValue) {
     9 
    10         // 得到類對象
    11         Class<?> objClass = obj.getClass();
    12         // 得到類中的所有屬性集合
    13         Field[] fs = objClass.getDeclaredFields();
    14 
    15         for (Field f : fs) {
    16 
    17             // 設置些屬性是可以訪問的
    18             f.setAccessible(true);
    19             try {
    20 
    21                 if (f.getName().endsWith(key)) {
    22                     if (newValue.equalsIgnoreCase(f.get(obj).toString())) {
    23                         f.set(obj, key);
    24                     }
    25                 }
    26 
    27             } catch (IllegalArgumentException | IllegalAccessException e) {
    28                 e.printStackTrace();
    29             }
    30         }
    31     }

    View Code

    (2)測試

    

     1 public static void main(String[] args) {
     2 
     3         Object[] objects = new Object[5];
     4         UserVO userVO = new UserVO("zhansan", "888");
     5         objects[0] = userVO;
     6         objects[1] = new Date();
     7 
     8 
     9         changeObjectValueByKey(objects[0], "name", "lisi");
    10         System.out.println("user: " + new Gson().toJson(objects));
    11 }

    View Code

    4、根據傳入的索引，修改object[]中的對象的值

    (1)方法

    

     1 public static void changeObjectValue(Object[] obj, int index, String newValue) {
     2 
     3         for (int i = 0; i < obj.length; i++) {
     4 
     5             if (i == index) {
     6 
     7                 if (obj[i] instanceof Object[]) {
     8                     Object[] objects = (Object[]) obj[i];
     9                     objects[0] = newValue;
    10                 }
    11             }
    12         }
    13     }

    View Code

    (2)測試

    

     1 public static void main(String[] args) {
     2 
     3         Object[] objects = new Object[5];
     4         UserVO userVO = new UserVO("zhansan", "888");
     5         objects[0] = userVO;
     6         objects[1] = new Date();
     7 
     8 
     9         changeObjectValue(objects, 0, "lisi");
    10         System.out.println("user: " + new Gson().toJson(objects));
    11 }

    View Code

    5、修改object中的值

    (1)方法

    

     1 public static String getChildValueFromList(Object[] obj, int index) {
     2 
     3         for (int i = 0; i < obj.length; i++) {
     4 
     5             if (i == index) {
     6 
     7                 if (obj[i] instanceof Object[]) {
     8                     Object[] objects = (Object[]) obj[i];
     9                     return objects[0].toString();
    10                 }
    11             }
    12         }
    13 
    14 
    15         return "";
    16     }

    View Code

    (2)測試

    

     1 public static void main(String[] args) {
     2 
     3         Object[] objects = new Object[5];
     4         UserVO userVO = new UserVO("zhansan", "888");
     5         objects[0] = userVO;
     6         objects[1] = new Date();
     7 
     8         String childValue = getChildValueFromList(objects, 2);
     9         System.out.println("childValue: " + childValue);
    10 }

    View Code