Java List Object[]转换成List T的实例

一）背景

主要是为了实现数据之间的转换，方便数据展示。

使用场景：当数据可能是List类型，可能会需要转换成具体的List格式。

二）List转换成List

功能：传入List数据和需要转换的Class对象，返回一个List数据集合

实现方式：Java反射方式，使用的是构造器的方式

缺点：实体类中必须有无参数构造器，有参数构造器，且构造器参数的顺序和数据的顺序必须一致。如果数据格式有变化，需要重新编写一个实体类的构造器

实现源码：

package com.oysept.utils; 
import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.List;
 

public class ObjectToBeanUtils {
 
 
 public static  List objectToBean(List objList, Class clz) throws Exception{
  if (objList==null || objList.size()==0) {
   return null;
  }
 
  Class[] cz = null;
  Constructor[] cons = clz.getConstructors();
  for (Constructor ct : cons) {
   Class[] clazz = ct.getParameterTypes();
   if (objList.get(0).length == clazz.length) {
    cz = clazz;
    break;
   }
  }
 
  List list = new ArrayList();
  for (Object[] obj : objList) {
   Constructor cr = clz.getConstructor(cz);
   list.add(cr.newInstance(obj));
  }
  return list;
 }
}

三）实体类PhoneVO.java

package com.oysept.bean;
 
import java.io.Serializable;
import java.math.BigDecimal; 
public class PhoneEntity implements Serializable { 
 private static final long serialVersionUID = 1L; 
 public PhoneEntity() {}
 
 
 public PhoneEntity(String plate, BigDecimal number, double memory, double size) {
  super();
  this.plate = plate;
  this.number = String.valueOf(number);
  this.memory = String.valueOf(memory);
  this.size = String.valueOf(size);
 }
 
 private String plate;
 private String number;
 private String memory;
 private String size;
 
 public String getPlate() { return plate; }
 public void setPlate(String plate) { this.plate = plate; }
 
 public String getNumber() { return number; }
 public void setNumber(String number) { this.number = number; }
 
 public String getMemory() { return memory; }
 public void setMemory(String memory) { this.memory = memory; }
 
 public String getSize() { return size; }
 public void setSize(String size) { this.size = size;}
}
 

四）数据转换测试类

package com.oysept.test;
 
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List; 
import com.oysept.bean.PhoneEntity;
import com.oysept.utils.ObjectToBeanUtils;
 

public class ObjectToBeanTest {
 
 public static void main(String[] args) throws Exception {
  // 初始化数据
  Object[] obj = new Object[4];
  obj[0] = "hw";
  obj[1] = BigDecimal.valueOf(13699999999L);
  obj[2] = 4.7;
  obj[3] = 5.0;
 
  Object[] obj1 = new Object[4];
  obj1[0] = "vivo";
  obj1[1] = BigDecimal.valueOf(13611111111L);
  obj1[2] = 4.8;
  obj1[3] = 5.7;
 
  List objList = new ArrayList();
  objList.add(obj);
  objList.add(obj1);
 
  // 工具类
  List list = ObjectToBeanUtils.objectToBean(objList, PhoneEntity.class);
  for (PhoneEntity phone : list) {
   System.out.println(phone.getPlate() + "t" + phone.getNumber()
    + "t" + phone.getMemory() + "t" + phone.getSize());
  }
 }
}

数据转换打印效果图：

补充知识：List、List＜Object＞、List＜?＞的区别

通过一个例子来比较这几种写法的区别

public class ListWithoutGeneric {
 public static void main(String[] args) {
  // 第一段：不使用泛型的方式
  List a1 = new ArrayList();
  a1.add(new Object());
  a1.add(new Integer(1));
  a1.add(new String("a1"));
 
  // 第二段：把a1赋值给List