java 值传递 对象复制

做项目时经常遇到 输出参数时值相变了？相互影响了 ？

java对象之间都是地址传递 所以要将对象值赋值过去 用BeanUtils里的对象复制工具BeanUtils.copyProperties(u, u1);

 

List<MlklUser> count1List = new ArrayList<MlklUser>();
List<MlklUser> count2List = new ArrayList<MlklUser>();
List<MlklUser> regDateList = new ArrayList<MlklUser>();
List<MlklUser> regOrderList = new ArrayList<MlklUser>();
List<MlklUser> regNoOrderList = new ArrayList<MlklUser>();


for (MlklUser u : list) {
MlklUser u1 = new MlklUser();
BeanUtils.copyProperties(u, u1);
if (u.getParent().getId().equals(user.getpIds())) {
count1++;
count1List.add(u);
} else if (u.getpIds().split(",").length == 3 && u.getpIds().split(",")[0].equals(user.getpIds())) {
count3++;
} else {
count2List.add(u);
}

 

 

（1）在Java里面参数传递都是按值传递”这句话的意思是：按值传递是传递的值的拷贝，按引用传递其实传递的是引用的地址值，所以统称按值传递。

（2）在Java里面只有基本类型和按照下面这种定义方式的String是按值传递，其它的都是按引用传递。

 

Android中Jdk被精简 会找不到一下复制工具类：

package com.samsung.galaxy.utils;
 
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
 

public class BeanPropertiesUtil {
    /**
     * 利用反射实现对象之间属性复制
     * @param from
     * @param to
     */
    public static void copyProperties(Object from, Object to) throws Exception {
        copyPropertiesExclude(from, to, null);
    }
 
    /**
     * 复制对象属性
     * @param from
     * @param to
     * @param excludsArray 排除属性列表
     * @throws Exception
     */
    @SuppressWarnings("unchecked")
    public static void copyPropertiesExclude(Object from, Object to, String[] excludsArray) throws Exception {
        List<String> excludesList = null;
        if(excludsArray != null && excludsArray.length > 0) {
            excludesList = Arrays.asList(excludsArray);    //构造列表对象
        }
        Method[] fromMethods = from.getClass().getDeclaredMethods();
        Method[] toMethods = to.getClass().getDeclaredMethods();
        Method fromMethod = null, toMethod = null;
        String fromMethodName = null, toMethodName = null;
        for (int i = 0; i < fromMethods.length; i++) {
            fromMethod = fromMethods[i];
            fromMethodName = fromMethod.getName();
            if (!fromMethodName.contains("get") || fromMethodName.contains("getId"))
                continue;
            //排除列表检测
            if(excludesList != null && excludesList.contains(fromMethodName.substring(3).toLowerCase())) {
                continue;
            }
            toMethodName = "set" + fromMethodName.substring(3);
            toMethod = findMethodByName(toMethods, toMethodName);
            if (toMethod == null)
                continue;
            Object value = fromMethod.invoke(from, new Object[0]);
            if(value == null)
                continue;
            //集合类判空处理
            if(value instanceof Collection) {
                Collection newValue = (Collection)value;
                if(newValue.size() <= 0)
                    continue;
            }
            toMethod.invoke(to, new Object[] {value});
        }
    }
 
    /**
     * 对象属性值复制，仅复制指定名称的属性值
     * @param from
     * @param to
     * @param includsArray
     * @throws Exception
     */
    @SuppressWarnings("unchecked")
    public static void copyPropertiesInclude(Object from, Object to, String[] includsArray) throws Exception {
        List<String> includesList = null;
        if(includsArray != null && includsArray.length > 0) {
            includesList = Arrays.asList(includsArray);    //构造列表对象
        } else {
            return;
        }
        Method[] fromMethods = from.getClass().getDeclaredMethods();
        Method[] toMethods = to.getClass().getDeclaredMethods();
        Method fromMethod = null, toMethod = null;
        String fromMethodName = null, toMethodName = null;
        for (int i = 0; i < fromMethods.length; i++) {
            fromMethod = fromMethods[i];
            fromMethodName = fromMethod.getName();
            if (!fromMethodName.contains("get"))
                continue;
            //排除列表检测
            String str = fromMethodName.substring(3);
            if(!includesList.contains(str.substring(0,1).toLowerCase() + str.substring(1))) {
                continue;
            }
            toMethodName = "set" + fromMethodName.substring(3);
            toMethod = findMethodByName(toMethods, toMethodName);
            if (toMethod == null)
                continue;
            Object value = fromMethod.invoke(from, new Object[0]);
            if(value == null)
                continue;
            //集合类判空处理
            if(value instanceof Collection) {
                Collection newValue = (Collection)value;
                if(newValue.size() <= 0)
                    continue;
            }
            toMethod.invoke(to, new Object[] {value});
        }
    }
 
 
 
    /**
     * 从方法数组中获取指定名称的方法
     *
     * @param methods
     * @param name
     * @return
     */
    public static Method findMethodByName(Method[] methods, String name) {
        for (int j = 0; j < methods.length; j++) {
            if (methods[j].getName().equals(name))
                return methods[j];
        }
        return null;
    }
}