如何在 java 中对此数组列表进行排序

Question

我正在使用OpenCsv访问我希望排序然后写回另一个文件名的fie。对列表进行排序时遇到问题。谢谢。

我正在尝试按第一列和第二列对 csv 文件进行排序。

 CSVReader reader = new CSVReader(new FileReader("d:\temp\data1.csv"), ',', '"', 1);
 //Read all rows at once
 List<String[]> allRows = reader.readAll();
 //Read CSV line by line and use the string array as you want
 for(String[] row : allRows){
    System.out.println(Arrays.toString(row));
 }
 *Arrays.sort(allRows.toArray());*
 CSVWriter writer = new CSVWriter(new FileWriter("d:\temp\data1sorted.csv"));
 writer.writeAll(allRows);
 //close the writer
 writer.close();

运行此代码时出现以下错误：

Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.lang.Comparable
    at java.util.ComparableTimSort.countRunAndMakeAscending(Unknown Source)
    at java.util.ComparableTimSort.sort(Unknown Source)
    at java.util.ComparableTimSort.sort(Unknown Source)
    at java.util.Arrays.sort(Unknown Source)
    at CompareCsv.main(CompareCsv.java:31)

Answer 1

这对

你有帮助吗？

public static void main(String args[]) {
            ArrayList<String> animalList = new ArrayList<String>();
        animalList.add("Dog");
        animalList.add("Cat");
        animalList.add("Snake");
        animalList.add("Bison");
        System.out.println("Before Sorting:");
        for (String tmpStr : animalList) {
            System.out.println(tmpStr);
        }
        // sorting
        Collections.sort(animalList);
        System.out.println("After Sorting:");
        for (String tmpStr : animalList) {
            System.out.println(tmpStr);
        }
    }

Answer 2

您可以实现比较器来实现您的目的并使用： https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#sort（java.util.List，%20java.util.Comparator）

Answer 3

目前尚不清楚您是希望行在它们内部排序还是相互比较。假设两者兼而有之;

for(String[] row : allRows)
{
   Arrays.sort(row);
}
Collections.sort(allRows, new Comparator()
{
    @Override
    public int compare(Object o1, Object o2)
    {
        String[] a = (String[])o1;
        String[] b = (String[])o2;
        return a[0].compareTo(b[0]); //you'll probably want some additional checking here.
    }
});