android中文件夹大小,Java保留小数点位数

private void initSDCard() {

File DianDiYunVideo = new File(Environment.getExternalStorageDirectory(),"文件名字");

try {

double folderSize = getFolderSize(DianDiYunVideo);

java.text.DecimalFormat df=new java.text.DecimalFormat("#.##");

offline_value.setText(df.format(folderSize)+"MB");

System.out.println("这里保留小数点两位:"+df.format(folderSize));

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

public static double getFolderSize(java.io.File file)throws Exception{

double size = 0;

java.io.File[] fileList = file.listFiles();

for (int i = 0; i < fileList.length; i++) {

if (fileList[i].isDirectory()){


size = size + getFolderSize(fileList[i]);

} else{


System.out.println("文件的名字是:"+fileList[i].getName());

size = size + fileList[i].length();

}

}

return size/1048576;

}

一

Long是长整型，怎么有小数，是double吧

java.text.DecimalFormat df=new java.text.DecimalFormat("#.##");

double d=3.14159;

System.out.println(df.format(d));

二

java.math.BigDecimal

BigDecimal bd = new BigDecimal("3.14159265");

bd = bd.setScale(2,BigDecimal.ROUND_HALF_UP);

三

class Test1{

public static void main(String[] args){

double ret = convert(3.14159);



System.out.println(ret);

}



static double convert(double value){

long l1 = Math.round(value*100); //四舍五入

double ret = l1/100.0; //注意：使用 100.0 而不是 100

return ret;

}

}

四

double d = 13.4324;

d=((int)(d*100))/100;

你可以通过这个链接引用该篇文章:http://jxcn.bokee.com/tb.b?diaryId=14529336