//正常版:
import java.text.DecimalFormat;
import java.math.RoundingMode;

 DecimalFormat formater = new DecimalFormat();

 formater.setMaximumFractionDigits(2);
 formater.setGroupingSize(0);
 formater.setRoundingMode(RoundingMode.FLOOR);

 System.out.println(formater.format(123456.7897456));

// 简化版:(这个是四色五入,本人亲测.)
import java.text.DecimalFormat;

 DecimalFormat formater = new DecimalFormat("#0.##");
 System.out.println(formater.format(123456.7897456));