在 Java 中使用 for 循环创建映射时，Kep 的值始终保持 0

Question

我正在尝试对Map<String, Map<String, Object>>进行Map<String, Object>。

下面是代码：

Map<String, Object> createmap = new HashMap<String, Object>();
Map<String, Object> result = new HashMap<String, Object>();
for (int j=0 ; j<jsonarr2.size(); j++ )
{
    JSONObject jsonobj2 = (JSONObject) jsonarr2.get(j);
    Iterator<String> key2 = jsonobj2.keySet().iterator();
    while (key2.hasNext()) {
        String k2 = key2.next();
        createmap.put(k2, jsonobj2.get(k2));    
    }
    System.out.println("Print J:" + j + " CREATE MAP:" + createmap);
    result.put(Integer.toString(j),createmap);
    System.out.println("result :" + result);
}

For 循环运行 5 次，创建映射中将有 5 条记录。但是地图result始终使用键作为 0，因此result地图中只有createmap的最后一条记录可用。

循环内打印语句的输出：

Print J:0 CREATE MAP:{vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0001","timestamp":1548643752}}}}
result : {0={vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0001","timestamp":1548643752}}}}}
Print J:1 CREATE MAP:{vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0002","timestamp":1548643752}}}}
result : {0={vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0002","timestamp":1548643752}}}}}
Print J:2 CREATE MAP:{vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0003","timestamp":1548643752}}}}
result : {0={vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0003","timestamp":1548643752}}}}}
Print J:3 CREATE MAP:{vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0004","timestamp":1548643752}}}}
result : {0={vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0004","timestamp":1548643752}}}}}
Print J:4 CREATE MAP:{vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0005","timestamp":1548643752}}}}
result : {0={vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0005","timestamp":1548643752}}}}}

但最后的Map只有

{0={vsan_name={"value":{"0":{"sequence":0,"value":"VSAN0005","timestamp":1548643752}}}}}

键始终保持为 0，并且值正在更新为同一键。

Answer 1

看起来jsonarr2.size()是 1，因此，循环只运行一次（即使嵌套的JSONObject有 5 个键。

此外，您可能会从 json 数组的不同 json 对象中获取具有相同键的记录。尝试在for循环中移动createMap的实例化，例如：

Map<String, Object> result = new HashMap<String, Object>();
for (int j=0 ; j<jsonarr2.size(); j++ )
{
    Map<String, Object> createmap = new HashMap<String, Object>();
    JSONObject jsonobj2 = (JSONObject) jsonarr2.get(j);
    Iterator<String> key2 = jsonobj2.keySet().iterator();
    while (key2.hasNext()) {
        String k2 = key2.next();
        createmap.put(k2, jsonobj2.get(k2));    
    }
    System.out.println("Print J:" + j + " CREATE MAP:" + createmap);
    result.put(Integer.toString(j),createmap);
}