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

 class FunctionType {

     private String functionType;

     private Object[] objects;

     private boolean isDistinct;

     public String getFunctionType() {
         return functionType;
     }

     public void setFunctionType(String functionType) {
         this.functionType = functionType;
     }

     public Object[] getObjects() {
         return objects;
     }

     public void setObjects(Object[] objects) {
         this.objects = objects;
     }

     public boolean isDistinct() {
         return isDistinct;
     }

     public void setDistinct(boolean distinct) {
         isDistinct = distinct;
     }

     @Override
     protected Object clone() {

         FunctionType functionTypeDemo = new FunctionType();

         if (objects != null) {
             functionTypeDemo.setObjects(objects.clone());
         }

         functionTypeDemo.setFunctionType(functionType);

         functionTypeDemo.setDistinct(isDistinct);

         return functionTypeDemo;
     }
 }

2、创建测试数据

         FunctionType functionType = new FunctionType();

         functionType.setDistinct(false);
         functionType.setFunctionType("max");
         Object[] objects2 = new Object[1];
         objects2[0] = "mintime";
         functionType.setObjects(objects2);

         FunctionType functionType2 = new FunctionType();

         functionType2.setFunctionType("from_unixtime");
         functionType2.setDistinct(false);
         Object[] objects3 = new Object[2];
         objects3[0] = functionType;
         objects3[1] = "yyyy-MM-dd HH24:mi:ss";

         functionType2.setObjects(objects3);

3、创建修改方法

  private static void changeObjectParam(FunctionType functionType2, String string) {
         Object[] objects = functionType2.getObjects();

         // 替换
         Object[] replace = new Object[1];
         replace[0] = new String(string);

         for (int i = 0; i < objects.length; i++) {
             if (objects[0] instanceof FunctionType) {
                 FunctionType o = (FunctionType) objects[0];
                 if("max".equalsIgnoreCase(o.getFunctionType())){
                     if("mintime".equalsIgnoreCase(o.getObjects()[0].toString())){
                         o.setObjects(replace);
                     }
                 }

                 break;
             }
         }

         System.out.println(new Gson().toJson(functionType2));
     }

4、测试

 public static void main(String[] args) {

         FunctionType functionType = new FunctionType();

         functionType.setDistinct(false);
         functionType.setFunctionType("max");
         Object[] objects2 = new Object[1];
         objects2[0] = "mintime";
         functionType.setObjects(objects2);

         FunctionType functionType2 = new FunctionType();

         functionType2.setFunctionType("from_unixtime");
         functionType2.setDistinct(false);
         Object[] objects3 = new Object[2];
         objects3[0] = functionType;
         objects3[1] = "yyyy-MM-dd HH24:mi:ss";

         functionType2.setObjects(objects3);

         String string ="replace";

         // 修改mintime为maxtime
         // 修改mintime为maxtime
         changeObjectParam(functionType2, string);

     }

• 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

    

     /**
          * 获取object中存的值
          *
          * @param obj 传入的Object
          * @param key 传入的字段名称
          * @return 获取object中存的值
          */
         public static String getValueByKey(Object obj, String key) {
    
             // 得到类对象
             Class<?> objClass = obj.getClass();
             // 得到类中的所有属性集合
             Field[] fs = objClass.getDeclaredFields();
    
             for (Field f : fs) {
    
                 // 设置些属性是可以访问的
                 f.setAccessible(true);
    
                 try {
    
                     if (f.getName().endsWith(key)) {
                         return f.get(obj).toString();
                     }
    
                 } catch (IllegalArgumentException | IllegalAccessException e) {
                     e.printStackTrace();
                 }
             }
    
             return "";
         }

    (2)测试

    

     public static void main(String[] args) {
    
             Object[] objects = new Object[5];
             UserVO userVO = new UserVO("zhansan", "888");
             objects[0] = userVO;
             objects[1] = new Date();
             // name 是UserVO对象的字段属性名
             String name = getValueByKey(objects[0], "name");
             System.out.println("value: " + name);
     }

    2、根据传入的值，获取object中存的key

    (1)方法

    

     /**
          * 获取object中存的关键字
          *
          * @param obj 传入的Object
          * @return 获取object中存的关键字
          */
         public static String getKey(Object obj) {
    
             // 得到类对象
             Class<?> objClass = obj.getClass();
             // 得到类中的所有属性集合
             Field[] fs = objClass.getDeclaredFields();
    
             for (Field f : fs) {
    
                 // 设置些属性是可以访问的
                 f.setAccessible(true);
    
                 try {
    
                     return f.getName();
    
                 } catch (IllegalArgumentException e) {
                     e.printStackTrace();
                 }
             }
    
             return "";
         }

    (2)测试

    

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

    3、根据传入的key，修改object[]中的对象的值

    (1)方法

    

     /**
          * 修改object中参数的值
          *
          * @param obj      传入的Object
          * @param key      传入的字段名称
          * @param newValue 改变的值
          */
         public static void changeObjectValueByKey(Object obj, String key, String newValue) {
    
             // 得到类对象
             Class<?> objClass = obj.getClass();
             // 得到类中的所有属性集合
             Field[] fs = objClass.getDeclaredFields();
    
             for (Field f : fs) {
    
                 // 设置些属性是可以访问的
                 f.setAccessible(true);
                 try {
    
                     if (f.getName().endsWith(key)) {
                         if (newValue.equalsIgnoreCase(f.get(obj).toString())) {
                             f.set(obj, key);
                         }
                     }
    
                 } catch (IllegalArgumentException | IllegalAccessException e) {
                     e.printStackTrace();
                 }
             }
         }

    (2)测试

    

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

    4、根据传入的索引，修改object[]中的对象的值

    (1)方法

    

     public static void changeObjectValue(Object[] obj, int index, String newValue) {
    
             for (int i = 0; i < obj.length; i++) {
    
                 if (i == index) {
    
                     if (obj[i] instanceof Object[]) {
                         Object[] objects = (Object[]) obj[i];
                         objects[0] = newValue;
                     }
                 }
             }
         }

    (2)测试

    

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

    5、修改object中的值

    (1)方法

    

     public static String getChildValueFromList(Object[] obj, int index) {
    
             for (int i = 0; i < obj.length; i++) {
    
                 if (i == index) {
    
                     if (obj[i] instanceof Object[]) {
                         Object[] objects = (Object[]) obj[i];
                         return objects[0].toString();
                     }
                 }
             }
    
             return "";
         }

    (2)测试

    

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