与嵌套哈希图有关的问题

Question

I am writing a code in which there is a nested hashmap everything is fine while adding child to parent all the values of the different keys are getting overriden by the last key's value. Please suggest some solution ASAP. Thanks in advance below is the code.

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);     
        }    
    }
}

The output i am getting is like:

In first iteration

{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}}

Insecond iteration

{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

You need to either copy provData when you put it into provNextAndNetLoc or make a new provData on each iteration of the loop. For example:

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

The problem is that you don't create a new provData-Map for each cycle. So you change always the same instance of the Map during each iteration and put it in provNetAndNetLoc.

I would suggest that you create a new instance in provData in each cycle.

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