[英]How to sort a multi-dimensional Arraylist “ArrayList<String[]>” in Java?
我編寫了一個代碼,用每個String[]
的第一個元素對多維ArrayList ArrayList<String[]>
進行排序,2dArray如下所示:
{
["Mark", "mark@mail.com"],
["Angela", "zzAngela@gmail.com"],
["Harry", "abc_harry@hotmail.com"],
["Donald","donny@aol.com"]
}
但是當我運行代碼時數組沒有被排序,有人可以解釋我的代碼有什么問題嗎? 謝謝你!
ArrayList<String[]> sorter = new ArrayList<String[]>();
String file_name = "db_email.csv";
// READING FROM CSV FILE & STORING DATA INTO 2dARRAY
try{
BufferedReader reader = new BufferedReader(new FileReader (file_name));
String line = reader.readLine(); // read the rest
String[] row;
while(line != null){
String[] result = line.split(",");
sorter.add(new String[]{result[0], result[1]});
line = reader.readLine();
}
reader.close();
} catch (IOException e){
System.out.println(e);
}
// MY SORTING ALGORITHM
Collections.sort(sorter, new Comparator<String[]>() {
@Override
public int compare(String[] o1, String[] o2) {
return o1[0].compareTo(o2[0]);
}
});
// EXPECTED RESULT (sorting 2dArray by 1st column):
{
["Angela", "zzAngela@gmail.com"],
["Donald","donny@aol.com"],
["Harry", "abc_harry@hotmail.com"],
["Mark", "mark@mail.com"]
}
// ACTUAL RESULT (the array doesn't get sorted):
{
["Mark", "mark@mail.com"],
["Angela", "zzAngela@gmail.com"],
["Harry", "abc_harry@hotmail.com"],
["Donald","donny@aol.com"]
}
我終於解決了這個問題,我通過添加像“aaaaa,myname @ mail.com”這樣的行來測試排序算法。 我不知道大寫問題(可能是因為它比較了數值的Unicode值),因此上面的行總是放在最后。 當我用像Peter White,peter @ me.com這樣的普通線進行測試時,它按預期工作。
謝謝大家的幫助和建議!
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