java两个map合并

先贴出自己造数据的代码：
Map<String, Object> all = new LinkedHashMap<String, Object>();
List<Object> list = new ArrayList<Object>();
// 第一个map数据
Map<String, String> m1 = new LinkedHashMap<String, String>();
Map<String, String> m2 = new LinkedHashMap<String, String>();
Map<String, String> m3 = new LinkedHashMap<String, String>();
Map<String, String> m4 = new LinkedHashMap<String, String>();
m1.put("租金", "2013-01-01");
m2.put("租金", "2013-01-31");
m3.put("租金", "1516,1508,1502,1512,1510,1506");
m4.put("租金", "客户ID1");
list.add(m1);
list.add(m2);
list.add(m3);
list.add(m4);
all.put("合同1", list);
// 第二个map数据
list = new ArrayList<Object>();
m1 = new LinkedHashMap<String, String>();
m2 = new LinkedHashMap<String, String>();
m3 = new LinkedHashMap<String, String>();
m4 = new LinkedHashMap<String, String>();
m1.put("租金", "2013-01-01");
m2.put("租金", "2013-01-31");
m3.put("租金", "5A006,5A007,5A008");
m4.put("租金", "客户ID1");
list.add(m1);
list.add(m2);
list.add(m3);
list.add(m4);
all.put("合同2", list);

Map<String,Object> all2 = new LinkedHashMap<String, Object>();
//第三个map
list = new ArrayList<Object>();
m1 = new LinkedHashMap<String, String>();
m2 = new LinkedHashMap<String, String>();
m3 = new LinkedHashMap<String, String>();
m4 = new LinkedHashMap<String, String>();
m1.put("车位租金", "2013-01-01");
m2.put("车位租金", "2013-01-31");
m3.put("车位租金", "5A006");
m4.put("车位租金", "客户ID1");
list.add(m1);
list.add(m2);
list.add(m3);
list.add(m4);
all2.put("车位租金", list);

//第四个map
list = new ArrayList<Object>();
m1 = new LinkedHashMap<String, String>();
m2 = new LinkedHashMap<String, String>();
m3 = new LinkedHashMap<String, String>();
m4 = new LinkedHashMap<String, String>();
m1.put("广告位租金", "2013-09-01");
m2.put("广告位租金", "2013-09-30");
m3.put("广告位租金", "5A006");
m4.put("广告位租金", "客户ID1");
list.add(m1);
list.add(m2);
list.add(m3);
list.add(m4);
all2.put("广告位租金", list);
System.out.println(all);
System.out.println(all2);
打印出来的数据：
{合同1=[{租金=2013-01-01}, {租金=2013-01-31}, {租金=1516,1508,1502,1512,1510,1506}, {租金=客户ID1}],

合同2=[{租金=2013-01-01}, {租金=2013-01-31}, {租金=5A006,5A007,5A008}, {租金=客户ID1}]}

{车位租金=[{车位租金=2013-01-01}, {车位租金=2013-01-31}, {车位租金=5A006}, {车位租金=客户ID1}],

广告位租金=[{广告位租金=2013-09-01}, {广告位租金=2013-09-30},
{广告位租金=5A006}, {广告位租金=客户ID1}]}
=====================
因为车位租金，广告位租金中两个map的值 {车位租金=5A006}, {车位租金=客户ID1}都包含在合同2的map中，所以需要把车位租金，广告位租金的两个map插入到合同2的map去？请教该怎么实现？？？