DecimalFormat

code:

        DecimalFormat df1 = new DecimalFormat("0.0");
        DecimalFormat df2 = new DecimalFormat("#.#");
        DecimalFormat df3 = new DecimalFormat("000.000");
        DecimalFormat df4 = new DecimalFormat("###.###");
        DecimalFormat df5 = new DecimalFormat("0.000%");

        System.out.println(df1.format(12.34));
        System.out.println(df2.format(12.34));
        System.out.println(df3.format(12.34));
        System.out.println(df4.format(12.34));
        System.out.println(df5.format(.0012));

output:

12.3
12.3
012.340
12.34
0.120%

也可以看看DecimalFormat的相关类，例如NumberFormat