comparator for LinkedHashMap

问题

i am making a program to read data from excel files and store them in tables. But since I am new to Comparators in Java i have difficulties in making one of them. Here is my issue, I have managed to read all the data from excel files as a string and store them in a table. But my project is to store them in table by ascending IDs. Can someone help me to create a Comparator to compare LinkedHashmaps and store them by their IDs? The data that I have to store is like the below:

ID  Name    Salary         
50  christine   2349000        
43  paulina 1245874        
54  laura   4587894

The code for parsing the data is the below:

private static LinkedHashMap parseExcelColumnTitles(List sheetData) {

    List list = (List) sheetData.get(0);
    LinkedHashMap < String, Integer > tableFields = new LinkedHashMap(list.size());
    for (int j = 0; j < list.size(); j++) {
        Cell cell = (Cell) list.get(j);
        tableFields.put(cell.getStringCellValue(), cell.getCellType());
    }

    return tableFields;

}

private static LinkedHashMap[] parseExcelColumnData(List sheetData) {

    LinkedHashMap[] tousRows = new LinkedHashMap[sheetData.size() - 1];
    for (int rowCounter = 1; rowCounter < sheetData.size(); rowCounter++) {

        List list = (List) sheetData.get(rowCounter);

        LinkedHashMap < String, Integer > tableFields = new LinkedHashMap(list.size());
        String str;
        String[] tousFields = new String[list.size()];

        int i = 0;

        for (int j = 0; j < list.size(); j++) {
            Cell cell = (Cell) list.get(j);
            if (cell != null) {
                if (cell.getCellType() == Cell.CELL_TYPE_NUMERIC) {
                    tableFields.put(String.valueOf(cell
                        .getNumericCellValue()), cell.getCellType());
                } else if (cell.getCellType() == Cell.CELL_TYPE_STRING) {
                    tableFields.put(cell.getStringCellValue(), cell
                        .getCellType());
                } else if (cell.getCellType() == Cell.CELL_TYPE_BOOLEAN) {
                    tableFields.put(String.valueOf(cell
                        .getBooleanCellValue()), cell.getCellType());
                }
            }

        }
        tousRows[rowCounter - 1] = tableFields;
    }

    return tousRows;

}

回答1:

you can use TreeMap instead of LinkedHashMap, because you dont want to retain the order of insertion, and for sorting TreeMap is better choice. Read this too Java TreeMap Comparator

回答2:

You can do a model like this:

public class Salary implements Comparable<Salary> {
    private Long id;
    private String name;
    private Double salary;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Double getSalary() {
        return salary;
    }

    public void setSalary(Double salary) {
        this.salary = salary;
    }

    @Override
    public int compareTo(Salary o) {
        if (o.getId() < this.id) {
            return -1;
        } else if (o.getId() > this.id) {
            return 1;
        }
        return 0;
    }
}

Then you can use Collections.sort(list) to order your LinkedHashMap

来源：https://stackoverflow.com/questions/16294134/comparator-for-linkedhashmap

标签

java

comparator

linkedhashmap