Class OpsRecord{
private String id;
private long sequenceNumber;
//implemented hashcode and equals method considering both id and version.
//So two OpsRecord are equal only if two OpsRecord has same id and sequenceNumber.
}
Class OpsCompleteRecord{
// This class has 20 class variables including id and sequenceNumber.
}
I have an existing Map
that has the following values. Assuming the values are coming from a random data source.
Map<OpsRecord, OpsCompleteRecord> sourceMap = new HashMap<>();
sourceMap.put(new OpsRecord("1","1"), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("1","3"), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("1","2"), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("2","2"), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("2","1"), new OpsCompleteRecord());
I want a target map that should contain only OpsCompleteRecord
whose id
is 1 and sequenceNumber
is 3 , and another one with id
=2 and sequenceNumber
=2. [Latest sequenceNumber
for a id
]
targetMap
new OpsRecord("1","3"), new OpsCompleteRecord()
new OpsRecord("2","2"), new OpsCompleteRecord()
I am trying to implement with the below logic and code. Need your help in populating targetMap. I think I am messing up with the logic.
public static void main(String[] args) {
Map<OpsRecord, OpsCompleteRecord> sourceMap = new HashMap<>();
sourceMap.put(new OpsRecord("1","1"), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("1","3"), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("1","2"), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("2","2"), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("2","1"), new OpsCompleteRecord());
// Populate the target map
Map<OpsRecord, OpsCompleteRecord> targetMap = new HashMap<>();
Iterator<OpsRecord> itr = sourceMap.keySet().iterator();
while(itr.hasNext()){
OpsRecord opsRecord = itr.next();
// Iterate over targetMap.keySet().
// Take each key.getId()
// Compare targetMap key.getId() with opsRecord.getId()
// and if equal then Compare targetMap key.getSequenceNumber() with opsRecord.getSequenceNumber()
// if getSequenceNumber is small in targetMap, overwrite the object else ignore.
// else if all key.getId() is not equal to opsRecord.getId() then add that key and value to targetMap
}
}
I am using Java7.
In Java7 , maybe you can try to use guava Maps.filterKeys
, like:
Map<OpsRecord, OpsCompleteRecord> sourceMap = new HashMap();
sourceMap.put(new OpsRecord("1", 1), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("1", 3), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("1", 2), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("2", 2), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("2", 1), new OpsCompleteRecord());
Map<OpsRecord, OpsCompleteRecord> targetMap = Maps.filterKeys(sourceMap, new Predicate<OpsRecord>() {
@Override
public boolean apply(OpsRecord input) {
return input.id.equals(Long.toString(input.sequenceNumber));
}
});
In Java8 , you can use stream
with filter
and collector
can easy to do this:
sourceMap.put(new OpsRecord("1", 1), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("1", 3), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("1", 2), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("2", 2), new OpsCompleteRecord());
sourceMap.put(new OpsRecord("2", 1), new OpsCompleteRecord());
Map<OpsRecord, OpsCompleteRecord> targetmap =
sourceMap.entrySet().stream()
.filter(i -> i.getKey().id.equals(Long.toString(i.getKey().sequenceNumber)))
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
another thing need to call out: sequenceNumber
is long
type, so it should use new OpsRecord("2", 1)
.
Hopefully, it's helpful.
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