==========================================数字格式化工具

import java.math.BigDecimal;

public class DecimalFormatUtil {
    
    public static int ROUND_HALF_UP = BigDecimal.ROUND_HALF_UP;//四舍五入，舍弃部分如果大于等于5就进位，小于5的直接舍弃
    public static int ROUND_HALF_DOWN = BigDecimal.ROUND_HALF_DOWN;//五舍六入，舍弃部分如果大于5才进位，小于或等于5直接舍弃
    public static int ROUND_HALF_EVEN = BigDecimal.ROUND_HALF_EVEN;
    public static int ROUND_UP = BigDecimal.ROUND_UP;//舍弃部分如果大于等于1，就进位，否则舍弃
    public static int ROUND_DOWN = BigDecimal.ROUND_DOWN;//直接截取，不进位
    public static int ROUND_FLOOR = BigDecimal.ROUND_FLOOR;
    public static int ROUND_CEILING = BigDecimal.ROUND_CEILING;
    public static int ROUND_UNNECESSARY = BigDecimal.ROUND_UNNECESSARY;
    
    /**
     * 整数格式化（最后一位四舍五入）
     * @param input
     * @param roundingMode
     * @return
     */
    public static String longFormat(BigDecimal input) {
        return longFormat(input, ROUND_HALF_UP);
    }
    
    /**
     * 整数格式化
     * @param input
     * @param roundingMode
     * @return
     */
    public static String longFormat(BigDecimal input, int roundingMode) {
        BigDecimal outputDeci = input.setScale(0, roundingMode);
        return outputDeci.toString();
    }
    
    /**
     * 数字格式化（保留2位小数，最后一位四舍五入）
     * @param inputDouble
     * @return
     */
    public static String format(BigDecimal input){
        return format(input, 2, ROUND_HALF_UP);
    }
    
    /**
     * 数字格式化
     * @param input
     * @param scale
     * @param roundingMode
     * @return
     */
    public static String format(BigDecimal input, int scale, int roundingMode){
        BigDecimal outputDeci = input.setScale(scale, roundingMode);
        return outputDeci.toString();
    }
    
    /**
     * 百分数转换（两位小数，最后一位四舍五入）
     * @param inputStr
     * @return
     */
    public static String formatPercent(BigDecimal input){
        return formatPercent(input, 2, ROUND_HALF_UP);
    }
    
    /**
     * 百分数转换
     * @param input
     * @param scale 小数位
     * @param round 进位方式
     * @return
     */
    public static String formatPercent(BigDecimal input, int scale, int roundingMode){
        BigDecimal inputPerent = input.multiply(new BigDecimal(100));
        BigDecimal outputPerent = inputPerent.setScale(scale, roundingMode);
        return new StringBuffer(outputPerent.toString()).append("%").toString();
    }
}

==========================================数字格式化工具测试类

    /**
     * 整数格式化
     */
    @Test
    public void test_longFormat() {
        BigDecimal input = new BigDecimal("2.645");
        String format1 = DecimalFormatUtil.longFormat(input, DecimalFormatUtil.ROUND_HALF_UP);
        System.out.println(format1);
        String format2 = DecimalFormatUtil.longFormat(input);
        System.out.println(format2);
    }
    
    /**
     * 数字格式化
     */
    @Test
    public void test_format() {
        BigDecimal input = new BigDecimal("2.345");
        String format1 = DecimalFormatUtil.format(input, 2, DecimalFormatUtil.ROUND_HALF_UP);
        System.out.println(format1);
        String format2 = DecimalFormatUtil.format(input);
        System.out.println(format2);
    }
    
    /**
     * 百分数转换
     */
    @Test
    public void test_formatPercent(){
        BigDecimal input = new BigDecimal("2.3");
        String formatPercent1 = DecimalFormatUtil.formatPercent(input, 2, DecimalFormatUtil.ROUND_HALF_UP);
        System.out.println(formatPercent1);
        String formatPercent2 = DecimalFormatUtil.formatPercent(input);
        System.out.println(formatPercent2);
    }