java 怎样 改变 数组元素的值

时间：2024-01-27 08:21:37

java 怎样 改变 数组元素的值

  • 简介 （Introduction）：

    •  背景 需要解析Object数组中的数据,将数据(mintime)进行修改,改为(maxtime),修改后,生成新的对象

    • 结构图

    •  核心 对于Object数组的概念理解,对于数组的解析理解,数组赋值的理解 详见:https://www.cnblogs.com/liuyangfirst/p/12364850.html

    •  快速上手（Getting Started）

测试数据
1、创建测试对象
 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、创建测试数据
 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、创建修改方法
 1  private static void changeObjectParam(FunctionType functionType2, String string) {
 2         Object[] objects = functionType2.getObjects();
 3 
 4 
 5         // 替换
 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、测试
 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为maxtime
25         // 修改mintime为maxtime
26         changeObjectParam(functionType2, string);
27 
28 
29     }
View Code

  •  环境 JDK1.8

    •  配置 IDEA编辑

    •  存在问题 暂无

    •  进阶篇 （Advanced）：
      拓展object[]数据操作方法
      1、根据传入的key，获取object中存的值
      (1)方法

       1 /**
 2      * 获取object中存的值
 3      *
 4      * @param obj 传入的Object
 5      * @param key 传入的字段名称
 6      * @return 获取object中存的值
 7      */
 8     public static String getValueByKey(Object obj, String key) {
 9 
10         // 得到类对象
11         Class<?> objClass = obj.getClass();
12         // 得到类中的所有属性集合
13         Field[] fs = objClass.getDeclaredFields();
14 
15         for (Field f : fs) {
16 
17             // 设置些属性是可以访问的
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)测试
       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对象的字段属性名
 8         String name = getValueByKey(objects[0], "name");
 9         System.out.println("value: " + name);
10 }
      View Code
      2、根据传入的值，获取object中存的key
      (1)方法
       1 /**
 2      * 获取object中存的关键字
 3      *
 4      * @param obj 传入的Object
 5      * @return 获取object中存的关键字
 6      */
 7     public static String getKey(Object obj) {
 8 
 9         // 得到类对象
10         Class<?> objClass = obj.getClass();
11         // 得到类中的所有属性集合
12         Field[] fs = objClass.getDeclaredFields();
13 
14         for (Field f : fs) {
15 
16             // 设置些属性是可以访问的
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)测试
       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、根据传入的key，修改object[]中的对象的值
      (1)方法
       1 /**
 2      * 修改object中参数的值
 3      *
 4      * @param obj      传入的Object
 5      * @param key      传入的字段名称
 6      * @param newValue 改变的值
 7      */
 8     public static void changeObjectValueByKey(Object obj, String key, String newValue) {
 9 
10         // 得到类对象
11         Class<?> objClass = obj.getClass();
12         // 得到类中的所有属性集合
13         Field[] fs = objClass.getDeclaredFields();
14 
15         for (Field f : fs) {
16 
17             // 设置些属性是可以访问的
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)测试
       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、根据传入的索引，修改object[]中的对象的值
      (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)测试
       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)测试
       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

       

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