排序图<String, Object[]>

Question

I've created user defined Map ie

Map<String, Object[]> pass = new TreeMap<String, Object[]>();

Here I'm adding data to it inside for loop as shown below.

int row = 0;

 row++; 
 pass.put(row + "", new Object[] {"Data 1 : ","A"});
 row++;
 pass.put(row + "", new Object[] {"Data 2:", "B"});
 row++;
 pass.put(row + "", new Object[] {"Data 3:", "C"});
 row++;
 pass.put(row + "", new Object[] {"Data 4:", "D"});

But this data is not same as added order. Map is storing these data in random order. But I want these data in order. What needs to be done?

Answer 1

The TreeMap will sort your keys in their natural order (unless you inject a specific Comparator in its constructor).

In this case, it will use the lexicographical order for String s.

Lexicographical order implies that:

• 1 will come before 2 , but
• 10 will come before 2 as well !

If you need your keys to be sorted in numerical order, use Integer (or any Number ) for a key.

If instead, you need to retain the insertion order and don't care about sorting keys, you can use a LinkedHashMap .

As Keith points out, here 's the Java documentation for lexicographic String comparison.