我想在哈希图中添加相同键的值。例如:
ABC --> 123
DEF --> 456
ABC --> 123
XXX --> 111
XXX --> 222
应该变成:
ABC --> 246
DEF --> 456
XXX --> 333
这是我到目前为止的代码:
public class Reading {
@SuppressWarnings("unchecked")
public static void main(String[] args) throws IOException {
//Create hashmap to store the the string and int in the excel sheet
HashMap<String, Integer> hm = new HashMap<String, Integer>();
String key = null;
int value = Integer.MIN_VALUE;
// String chkeq; // this
@SuppressWarnings("rawtypes")
ArrayList list = new ArrayList();
// File path or EXCEL file
FileInputStream fos = new FileInputStream(
"/Users/SG/Desktop/tester.xls");
// Sheet is the individual sheet that the data is coming from, in this
// case Sheet1
try {
// Put the XLS file into
HSSFWorkbook workbook = new HSSFWorkbook(fos);
// Get first sheet from the project
HSSFSheet sheet = workbook.getSheetAt(0);
// Go through each row
Iterator<Row> rowIterator = sheet.iterator();
while (rowIterator.hasNext()) {
Row row = rowIterator.next();
// Go through each column in the rows
Iterator<Cell> cellIterator = row.cellIterator();
while (cellIterator.hasNext()) {
Cell cell = cellIterator.next();
switch (cell.getCellType()) {
case Cell.CELL_TYPE_BOOLEAN:
//System.out.print(cell.getBooleanCellValue() + "\t\t");
list.add(cell.getBooleanCellValue());
break;
case Cell.CELL_TYPE_NUMERIC:
//System.out.print(cell.getNumericCellValue() + "\t\t");
value = (int) cell.getNumericCellValue();
list.add(cell.getNumericCellValue());
break;
case Cell.CELL_TYPE_STRING:
//System.out.print(cell.getStringCellValue() + "\t\t");
key = cell.getStringCellValue();
//chkeq = cell.getStringCellValue();
/* for (int i = 0; cellIterator.hasNext(); i++) {
if (chkeq == cellIterator.next().getStringCellValue()) {
System.out.println("same" + cell.getStringCellValue());
}
}*/
list.add(cell.getStringCellValue());
break;
}
if (key != null && value != Integer.MIN_VALUE) {
hm.put(key, value);
key = null;
value = Integer.MIN_VALUE;
}
}
//System.out.println("");
}
for (String keys : hm.keySet())
System.out.println(keys + ":" + hm.get(keys));
fos.close();
// System.out.println(list);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
注意:我使用 Apache POI 从 Excel 工作表中提取数据。
代码输出如下:
DEF --> 456
ABC --> 123
XXX --> 222
所有这一切都是用相同的键覆盖放入散列映射中的最后一个单元格。
有什么方法可以对这些值求和而不是重写它们?
正如你所观察到的,hm.put
覆盖与该键关联的先前值(如果有)。 Java 8 中有一个新方法merges传入值与现有值。您可以使用 lambda 来指定如何完成合并。在这种情况下,合并操作是加法,所以我们会这样做:
hm.merge(key, value, (oldVal, newVal) -> oldVal + newVal);
在 Java 8 之前,您必须使用条件,如切鲁维安的回答. (+1)
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