與嵌套哈希圖有關的問題

Question

我正在寫一個代碼，其中有一個嵌套的哈希圖，一切都很好，同時將child添加到父項，所有不同鍵的值都被最后一個鍵的值覆蓋。 請盡快提出一些解決方案。 在此先感謝以下代碼。

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);     
        }    
    }
}

我得到的輸出是這樣的：

第一次迭代

{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}}

秒迭代

{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

您需要在將provData放入provNextAndNetLoc時復制provData，或在循環的每次迭代中創建一個新的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

問題是您沒有為每個周期創建一個新的provData-Map。 因此，您在每次迭代過程中始終更改Map的相同實例，並將其放入provNetAndNetLoc中。

我建議您在每個周期中在provData中創建一個新實例。

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