Java Collections.sort doesn't call compare method
I've read all answers etc, but non of them solved my problem.
I have basic function to sort list of custom object array by String InvoiceNumber.
List<Invoice> invoiceList = new ArrayList<>();
...
// invoiceList filled here
...
Collections.sort(invoiceList, new Comparator<Invoice>()
{
@Override
public int compare(Invoice o1, Invoice o2)
{
return o1.InvoiceNumber.compareTo(o2.InvoiceNumber);
}
});
Some part of Invoice class.
public class Invoice extends AttributeContainer
implements KvmSerializable,android.os.Parcelable, Comparable
{
public String CustomerId;
public String InvoiceNumber;
However, it never calls compare method.
I'm using android studio with latest libraries. Is there anything that I'm missing?
java sorting collections
asked Apr 25 '17 at 19:50
MmtBknMmtBkn
622925
|
show 12 more comments
I've read all answers etc, but non of them solved my problem.
I have basic function to sort list of custom object array by String InvoiceNumber.
List<Invoice> invoiceList = new ArrayList<>();
...
// invoiceList filled here
...
Collections.sort(invoiceList, new Comparator<Invoice>()
{
@Override
public int compare(Invoice o1, Invoice o2)
{
return o1.InvoiceNumber.compareTo(o2.InvoiceNumber);
}
});
Some part of Invoice class.
public class Invoice extends AttributeContainer
implements KvmSerializable,android.os.Parcelable, Comparable
{
public String CustomerId;
public String InvoiceNumber;
However, it never calls compare method.
I'm using android studio with latest libraries. Is there anything that I'm missing?
java sorting collections
asked Apr 25 '17 at 19:50
MmtBknMmtBkn
622925
7
How are you sure it never calls it?
– maszter
Apr 25 '17 at 19:57
3
Post the class / method which utilizes this comparator. We cannot determine why it's not being called (or if it's not even being called for that matter) with the little snippet of code you've posted.
– Jake Miller
Apr 25 '17 at 20:01
3
Are you sureinvoiceListhas at least 2 elements?
– Andy Turner
Apr 25 '17 at 20:01
1
It's confusing to seeInvoiceNumberspelled like a type name but used like a member variable. Which is it?
– Lew Bloch
Apr 25 '17 at 20:02
1
Note thatInvoiceshouldn't implementComparable, but ratherComparable<Invoice>. And you don't really need to implementComparable<Invoice>(orComparable) if you're providing aComparator; but you can, if you so desire.
– Andy Turner
Apr 25 '17 at 20:13
|
show 12 more comments
I've read all answers etc, but non of them solved my problem.
I have basic function to sort list of custom object array by String InvoiceNumber.
List<Invoice> invoiceList = new ArrayList<>();
...
// invoiceList filled here
...
Collections.sort(invoiceList, new Comparator<Invoice>()
{
@Override
public int compare(Invoice o1, Invoice o2)
{
return o1.InvoiceNumber.compareTo(o2.InvoiceNumber);
}
});
Some part of Invoice class.
public class Invoice extends AttributeContainer
implements KvmSerializable,android.os.Parcelable, Comparable
{
public String CustomerId;
public String InvoiceNumber;
However, it never calls compare method.
I'm using android studio with latest libraries. Is there anything that I'm missing?
java sorting collections
asked Apr 25 '17 at 19:50
MmtBknMmtBkn
622925
I've read all answers etc, but non of them solved my problem.
I have basic function to sort list of custom object array by String InvoiceNumber.
List<Invoice> invoiceList = new ArrayList<>();
...
// invoiceList filled here
...
Collections.sort(invoiceList, new Comparator<Invoice>()
{
@Override
public int compare(Invoice o1, Invoice o2)
{
return o1.InvoiceNumber.compareTo(o2.InvoiceNumber);
}
});
Some part of Invoice class.
public class Invoice extends AttributeContainer
implements KvmSerializable,android.os.Parcelable, Comparable
{
public String CustomerId;
public String InvoiceNumber;
However, it never calls compare method.
I'm using android studio with latest libraries. Is there anything that I'm missing?
java sorting collections
java sorting collections
asked Apr 25 '17 at 19:50
MmtBknMmtBkn
622925
asked Apr 25 '17 at 19:50
MmtBknMmtBkn
622925
edited Apr 25 '17 at 21:38
MmtBkn
asked Apr 25 '17 at 19:50
MmtBknMmtBkn
622925
asked Apr 25 '17 at 19:50
MmtBknMmtBkn
622925
asked Apr 25 '17 at 19:50
MmtBknMmtBkn
622925
622925
7
How are you sure it never calls it?
– maszter
Apr 25 '17 at 19:57
3
Post the class / method which utilizes this comparator. We cannot determine why it's not being called (or if it's not even being called for that matter) with the little snippet of code you've posted.
– Jake Miller
Apr 25 '17 at 20:01
3
Are you sureinvoiceListhas at least 2 elements?
– Andy Turner
Apr 25 '17 at 20:01
1
It's confusing to seeInvoiceNumberspelled like a type name but used like a member variable. Which is it?
– Lew Bloch
Apr 25 '17 at 20:02
1
Note thatInvoiceshouldn't implementComparable, but ratherComparable<Invoice>. And you don't really need to implementComparable<Invoice>(orComparable) if you're providing aComparator; but you can, if you so desire.
– Andy Turner
Apr 25 '17 at 20:13
|
show 12 more comments
7
How are you sure it never calls it?
– maszter
Apr 25 '17 at 19:57
3
Post the class / method which utilizes this comparator. We cannot determine why it's not being called (or if it's not even being called for that matter) with the little snippet of code you've posted.
– Jake Miller
Apr 25 '17 at 20:01
3
Are you sureinvoiceListhas at least 2 elements?
– Andy Turner
Apr 25 '17 at 20:01
1
It's confusing to seeInvoiceNumberspelled like a type name but used like a member variable. Which is it?
– Lew Bloch
Apr 25 '17 at 20:02
1
Note thatInvoiceshouldn't implementComparable, but ratherComparable<Invoice>. And you don't really need to implementComparable<Invoice>(orComparable) if you're providing aComparator; but you can, if you so desire.
– Andy Turner
Apr 25 '17 at 20:13
7
7
How are you sure it never calls it?
– maszter
Apr 25 '17 at 19:57
How are you sure it never calls it?
– maszter
Apr 25 '17 at 19:57
3
3
Post the class / method which utilizes this comparator. We cannot determine why it's not being called (or if it's not even being called for that matter) with the little snippet of code you've posted.
– Jake Miller
Apr 25 '17 at 20:01
Post the class / method which utilizes this comparator. We cannot determine why it's not being called (or if it's not even being called for that matter) with the little snippet of code you've posted.
– Jake Miller
Apr 25 '17 at 20:01
3
3
Are you sure
invoiceList has at least 2 elements?– Andy Turner
Apr 25 '17 at 20:01
Are you sure
invoiceList has at least 2 elements?– Andy Turner
Apr 25 '17 at 20:01
1
1
It's confusing to see
InvoiceNumber spelled like a type name but used like a member variable. Which is it?– Lew Bloch
Apr 25 '17 at 20:02
It's confusing to see
InvoiceNumber spelled like a type name but used like a member variable. Which is it?– Lew Bloch
Apr 25 '17 at 20:02
1
1
Note that
Invoice shouldn't implement Comparable, but rather Comparable<Invoice>. And you don't really need to implement Comparable<Invoice> (or Comparable) if you're providing a Comparator; but you can, if you so desire.– Andy Turner
Apr 25 '17 at 20:13
Note that
Invoice shouldn't implement Comparable, but rather Comparable<Invoice>. And you don't really need to implement Comparable<Invoice> (or Comparable) if you're providing a Comparator; but you can, if you so desire.– Andy Turner
Apr 25 '17 at 20:13
|
show 12 more comments
2 Answers
2
active
oldest
votes
However, it never calls compare method.
The only time that the compare(...) method would not be called is if your list has 0 or 1 items in it. Probably this is a debugging problem with Android and the compare(...) is being called but maybe the breakpoint is being skipped. Putting some sort of log messages inside of the method will confirm this.
I suspect that your problem is here:
public String InvoiceNumber;
First of all the field name should be invoiceNumber with a starting lowercase letter. Also it probably should not be public for data hiding reasons.
But I suspect that real problem is with String comparisons of numbers. For example if you have the following invoice-number strings in your entities:
1
2
3
10
11
20
25
114
201
Then these will sort like:
1
10
11
114
2
20
25
201
3
That's how the String.compare(...) method would sort it because the string "3" is greater than the string "201". If you want them to be sorted as numbers then you should make the invoiceNumber field be an int or long.
Hope this helps.
answered Apr 25 '17 at 22:08
GrayGray
96.5k14230300
Ohhh.. You're right!! There is debugging problem.
– MmtBkn
Apr 25 '17 at 22:12
add a comment |
I had the same problem when creating anonymous class for the sort method. Try to extract your Comparator class and you'll be able to debug.
answered Nov 24 '18 at 10:11
htafoyahtafoya
9,81194563
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
However, it never calls compare method.
The only time that the compare(...) method would not be called is if your list has 0 or 1 items in it. Probably this is a debugging problem with Android and the compare(...) is being called but maybe the breakpoint is being skipped. Putting some sort of log messages inside of the method will confirm this.
I suspect that your problem is here:
public String InvoiceNumber;
First of all the field name should be invoiceNumber with a starting lowercase letter. Also it probably should not be public for data hiding reasons.
But I suspect that real problem is with String comparisons of numbers. For example if you have the following invoice-number strings in your entities:
1
2
3
10
11
20
25
114
201
Then these will sort like:
1
10
11
114
2
20
25
201
3
That's how the String.compare(...) method would sort it because the string "3" is greater than the string "201". If you want them to be sorted as numbers then you should make the invoiceNumber field be an int or long.
Hope this helps.
answered Apr 25 '17 at 22:08
GrayGray
96.5k14230300
Ohhh.. You're right!! There is debugging problem.
– MmtBkn
Apr 25 '17 at 22:12
add a comment |
However, it never calls compare method.
The only time that the compare(...) method would not be called is if your list has 0 or 1 items in it. Probably this is a debugging problem with Android and the compare(...) is being called but maybe the breakpoint is being skipped. Putting some sort of log messages inside of the method will confirm this.
I suspect that your problem is here:
public String InvoiceNumber;
First of all the field name should be invoiceNumber with a starting lowercase letter. Also it probably should not be public for data hiding reasons.
But I suspect that real problem is with String comparisons of numbers. For example if you have the following invoice-number strings in your entities:
1
2
3
10
11
20
25
114
201
Then these will sort like:
1
10
11
114
2
20
25
201
3
That's how the String.compare(...) method would sort it because the string "3" is greater than the string "201". If you want them to be sorted as numbers then you should make the invoiceNumber field be an int or long.
Hope this helps.
answered Apr 25 '17 at 22:08
GrayGray
96.5k14230300
Ohhh.. You're right!! There is debugging problem.
– MmtBkn
Apr 25 '17 at 22:12
add a comment |
However, it never calls compare method.
The only time that the compare(...) method would not be called is if your list has 0 or 1 items in it. Probably this is a debugging problem with Android and the compare(...) is being called but maybe the breakpoint is being skipped. Putting some sort of log messages inside of the method will confirm this.
I suspect that your problem is here:
public String InvoiceNumber;
First of all the field name should be invoiceNumber with a starting lowercase letter. Also it probably should not be public for data hiding reasons.
But I suspect that real problem is with String comparisons of numbers. For example if you have the following invoice-number strings in your entities:
1
2
3
10
11
20
25
114
201
Then these will sort like:
1
10
11
114
2
20
25
201
3
That's how the String.compare(...) method would sort it because the string "3" is greater than the string "201". If you want them to be sorted as numbers then you should make the invoiceNumber field be an int or long.
Hope this helps.
answered Apr 25 '17 at 22:08
GrayGray
96.5k14230300
However, it never calls compare method.
The only time that the compare(...) method would not be called is if your list has 0 or 1 items in it. Probably this is a debugging problem with Android and the compare(...) is being called but maybe the breakpoint is being skipped. Putting some sort of log messages inside of the method will confirm this.
I suspect that your problem is here:
public String InvoiceNumber;
First of all the field name should be invoiceNumber with a starting lowercase letter. Also it probably should not be public for data hiding reasons.
But I suspect that real problem is with String comparisons of numbers. For example if you have the following invoice-number strings in your entities:
1
2
3
10
11
20
25
114
201
Then these will sort like:
1
10
11
114
2
20
25
201
3
That's how the String.compare(...) method would sort it because the string "3" is greater than the string "201". If you want them to be sorted as numbers then you should make the invoiceNumber field be an int or long.
Hope this helps.
answered Apr 25 '17 at 22:08
GrayGray
96.5k14230300
answered Apr 25 '17 at 22:08
GrayGray
96.5k14230300
answered Apr 25 '17 at 22:08
GrayGray
96.5k14230300
answered Apr 25 '17 at 22:08
GrayGray
96.5k14230300
96.5k14230300
Ohhh.. You're right!! There is debugging problem.
– MmtBkn
Apr 25 '17 at 22:12
add a comment |
Ohhh.. You're right!! There is debugging problem.
– MmtBkn
Apr 25 '17 at 22:12
Ohhh.. You're right!! There is debugging problem.
– MmtBkn
Apr 25 '17 at 22:12
Ohhh.. You're right!! There is debugging problem.
– MmtBkn
Apr 25 '17 at 22:12
add a comment |
I had the same problem when creating anonymous class for the sort method. Try to extract your Comparator class and you'll be able to debug.
answered Nov 24 '18 at 10:11
htafoyahtafoya
9,81194563
add a comment |
I had the same problem when creating anonymous class for the sort method. Try to extract your Comparator class and you'll be able to debug.
answered Nov 24 '18 at 10:11
htafoyahtafoya
9,81194563
add a comment |
I had the same problem when creating anonymous class for the sort method. Try to extract your Comparator class and you'll be able to debug.
answered Nov 24 '18 at 10:11
htafoyahtafoya
9,81194563
I had the same problem when creating anonymous class for the sort method. Try to extract your Comparator class and you'll be able to debug.
answered Nov 24 '18 at 10:11
htafoyahtafoya
9,81194563
answered Nov 24 '18 at 10:11
htafoyahtafoya
9,81194563
answered Nov 24 '18 at 10:11
htafoyahtafoya
9,81194563
answered Nov 24 '18 at 10:11
htafoyahtafoya
9,81194563
9,81194563
add a comment |
add a comment |
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7
How are you sure it never calls it?
– maszter
Apr 25 '17 at 19:57
3
Post the class / method which utilizes this comparator. We cannot determine why it's not being called (or if it's not even being called for that matter) with the little snippet of code you've posted.
– Jake Miller
Apr 25 '17 at 20:01
3
Are you sure
invoiceListhas at least 2 elements?– Andy Turner
Apr 25 '17 at 20:01
1
It's confusing to see
InvoiceNumberspelled like a type name but used like a member variable. Which is it?– Lew Bloch
Apr 25 '17 at 20:02
1
Note that
Invoiceshouldn't implementComparable, but ratherComparable<Invoice>. And you don't really need to implementComparable<Invoice>(orComparable) if you're providing aComparator; but you can, if you so desire.– Andy Turner
Apr 25 '17 at 20:13