Adding to unexpected arraylist behavior
I'm not sure what's going on here. Any enlightenment would be greatly appreciated.
ArrayList<Integer> al = new ArrayList<>();
for(int i = 0; i < 10; i++)
al.add(i);
for(Integer i : al)
System.out.println(al.get(i));
al.add(2,8); //should add the value 8 to index 2?
System.out.println();
for(Integer i : al)
System.out.println(al.get(i));
Output
0 1 2 3 4 5 6 7 8 9 0 1 7 8 2 3 4 5 6 7 8
Why does he add in 7 and 8 ... and where is 9?
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You get this behavior because you are calling get()
with itself Integer
, contained in ArrayList
:
for (Integer i : al)
System.out.println(al.get(i)); // i already contains the entry in the ArrayList
al.add(2,8); //should add the value 8 to index 2?
System.out.println();
for (Integer i : al)
System.out.println(al.get(i)); // again, i already contains the ArrayList entry
Change your code to this and you should be fine:
for (Integer i : al)
System.out.println(i);
Output:
0
1
8 <-- you inserted the number 8 at position 2 (third entry),
2 shifting everything to the right by one
3
4
5
6
7
8
9
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You use an extended loop and then print the value with get
; You must either print the values at all indices with get
, or use an extended loop without get
. Better yet, use Arrays.toString
for printing to avoid this kind of confusion:
for(int i = 0; i < 10; i++)
al.add(i);
Arrays.toString(al);
al.add(2,8);
Arrays.toString(al);
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