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Get keys from HashMap in Java
...HashMap contains more than one key. You can use keySet() to get the set of all keys.
team1.put("foo", 1);
team1.put("bar", 2);
will store 1 with key "foo" and 2 with key "bar". To iterate over all the keys:
for ( String key : team1.keySet() ) {
System.out.println( key );
}
will print "foo"...
How do I do an OR filter in a Django query?
...
@alexis: you could also do Item.objects.filter(creator__in=creators), for example.
– Kevin London
Dec 9 '14 at 23:11
4
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MongoDB with redis
...oDB does not have yet an expiration mechanism. Capped collections cannot really be used to implement a real TTL. Redis has a TTL-based expiration mechanism, making it convenient to store volatile data. For instance, user sessions are commonly stored in Redis, while user data will be stored and index...
Breakpoint on property change
...al object
var obj = {
someProp: 10
};
// save in another property
obj._someProp = obj.someProp;
// overwrite with accessor
Object.defineProperty(obj, 'someProp', {
get: function () {
return obj._someProp;
},
set: function (value) {
debugger; // sets breakpoint
...
Samples of Scala and Java code where Scala code looks simpler/has fewer lines?
I need some code samples (and I also really curious about them) of Scala and Java code which show that Scala code is more simple and concise then code written in Java (of course both samples should solve the same problem).
...
Java Error opening registry key
...er removing the "java" executables from my system32 folder, I had to reinstall the JRE. After that, my problem was solved. Thanks for the starting point.
– dangowans
Dec 24 '13 at 18:31
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How to use transactions with dapper.net?
...icitly roll back on error or does System.Transactions handle that automatically?
– Norbert Norbertson
Oct 3 '17 at 12:30
6
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Sort a list by multiple attributes?
... how, you can wrap your criteria (functions) in parenthesis:
s = sorted(my_list, key=lambda i: ( criteria_1(i), criteria_2(i) ), reverse=True)
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Error 1022 - Can't write; duplicate key in table
...ou can not have the same foreign key names in the database tables.
Check all your tables and all your foreign keys and avoid having two foreign keys with the same exact name.
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How to filter array in subdocument with MongoDB [duplicate]
...use $group to put it back together:
db.test.aggregate([
{ $match: {_id: ObjectId("512e28984815cbfcb21646a7")}},
{ $unwind: '$list'},
{ $match: {'list.a': {$gt: 3}}},
{ $group: {_id: '$_id', list: {$push: '$list.a'}}}
])
outputs:
{
"result": [
{
"_id": ObjectId("512...