java - 如何在 Java 中对 double 进行舍入？ (安卓开发)

Question

我正在使用以下方法从 SQLite 数据库返回值。

public String Totalsponsor() {
    // TODO Auto-generated method stub
    String[] columns = new String[] { KEY_SPONSOR, KEY_SWIMMERLAPS };
    Cursor c = ourDatabase.rawQuery("SELECT " + KEY_SWIMMERLAPS + " * "
            + KEY_SPONSOR + " AS result FROM " + DATABASE_TABLE  + " ORDER BY "+ KEY_SWIMMERLAPS+" DESC", null);

    String result = "";

    for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
        result = result + c.getDouble(0) + "\n";
    }

    return result;

}

在返回结果之前如何舍入结果？

我尝试过:

for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
结果 = 结果 + Math.round(c.getDouble(0)) + "\n";
}

但它似乎不起作用(也许我还没有理解舍入方法？)。

编辑:我似乎只得到了第一个结果。

Answer 1

DecimalFormat df = new DecimalFormat("####.##"); // here define you can define how much precision you want.

for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) { 
  result = result + df.format(c.getDouble(0)) + "\n"; 
}