Question

我正在编写一个代码，其中有一个嵌套的hashmap，一切正常，同时将child添加到parent，不同键的所有值都被最后一个键的值覆盖。请尽快提出一些解决方案。先谢谢，下面是代码。

Map<String, Object> provData = new HashMap<String, Object>();
Map<Integer, Map<String, Object>> provNetAndNetLoc =  new HashMap<Integer, Map<String, Object>>();

try {

    for (Integer provNetCycleId : provNetInfo) {

        this.provNetLocPs = jdbcShell.getJdbcConnection().prepareStatement(this.provNetLocQuery);
        this.provNetLocPs.setString(1,  tin);
        this.provNetLocPs.setInt(2,  provNetCycleId);
        this.provNetLocRs = this.provNetLocPs.executeQuery();

        while(this.provNetLocRs.next()){

            provData.put("netCycleStartDate", provNetLocRs.getDate("netCycleStartDate"));
            provData.put("netCycleEndDate", provNetLocRs.getDate("netCycleEndDate"));
            provData.put("netLocCycleId", provNetLocRs.getInt("netLocCycleId"));
            provData.put("netLocCycStartDate", provNetLocRs.getDate("netLocCycStartDate"));
            provData.put("netLocCycleEndDate", provNetLocRs.getDate("netLocCycleEndDate"));
            provData.put("locId", provNetLocRs.getInt("locId"));
            provData.put("locStartDate", provNetLocRs.getDate("locStartDate"));
            provData.put("locEndDate", provNetLocRs.getDate("locEndDate"));
            provData.put("provId", provNetLocRs.getInt("provId"));

            System.out.println("HashCode "+provData.hashCode());
            provNetAndNetLoc.put(provNetCycleId, provData);     
        }    
    }
}

我得到的输出就像：

在第一次迭代中

{85={locEndDate=4000-01-01, locStartDate=2000-01-01, netCycleStartDate=2014-03-01,      provId=87, netLocCycStartDate=2014-03-11, netLocCycleId=67, netLocCycleEndDate=4000-01-01, locId=106, netCycleEndDate=4000-01-01}}

非迭代

{85={locEndDate=4000-01-01, locStartDate=2014-03-15, netCycleStartDate=2013-03-01, provId=122, netLocCycStartDate=2014-03-01, netLocCycleId=70, netLocCycleEndDate=4000-01-01, locId=208, netCycleEndDate=4000-01-01},
 88={locEndDate=4000-01-01, locStartDate=2014-03-15, netCycleStartDate=2013-03-01, provId=122, netLocCycStartDate=2014-03-01, netLocCycleId=70, netLocCycleEndDate=4000-01-01, locId=208, netCycleEndDate=4000-01-01}}

Answer 1

当你将provData放入provNextAndNetLoc或者在循环的每次迭代中创建一个新的provData时，你需要复制provData。例如：

for (Integer provNetCycleId : provNetInfo) {
    this.provNetLocPs = jdbcShell.getJdbcConnection().prepareStatement(this.provNetLocQuery);
    this.provNetLocPs.setString(1,  tin);
    this.provNetLocPs.setInt(2,  provNetCycleId);
    this.provNetLocRs = this.provNetLocPs.executeQuery();

    while(this.provNetLocRs.next()){
        // because I create the map in the inner loop, I'll be loading each
        // result into a new map. When it was declared outside the loop, we 
        // kept referencing the same map instance and thus were overwriting it
        Map<String, Object> provData = new HashMap<String, Object>();


        provData.put("netCycleStartDate", provNetLocRs.getDate("netCycleStartDate"));
        provData.put("netCycleEndDate", provNetLocRs.getDate("netCycleEndDate"));
        provData.put("netLocCycleId", provNetLocRs.getInt("netLocCycleId"));
        provData.put("netLocCycStartDate", provNetLocRs.getDate("netLocCycStartDate"));
        provData.put("netLocCycleEndDate", provNetLocRs.getDate("netLocCycleEndDate"));
        provData.put("locId", provNetLocRs.getInt("locId"));
        provData.put("locStartDate", provNetLocRs.getDate("locStartDate"));
        provData.put("locEndDate", provNetLocRs.getDate("locEndDate"));
        provData.put("provId", provNetLocRs.getInt("provId"));

        System.out.println("HashCode "+provData.hashCode());
        provNetAndNetLoc.put(provNetCycleId, provData);


    }

Answer 2

问题是你不能为每个周期创建一个新的provData-Map。因此，您在每次迭代期间始终更改Map的相同实例，并将其放在provNetAndNetLoc中。

我建议你在每个周期的provData中创建一个新实例。

while(this.provNetLocRs.next()){
    provData = new HashMap<String, Object>();

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