java读写文件及保留指定位小数

public  static void main(String[] args)throws IOException{

double[][] B=new double[1043][21025];
double[][] transformB=new double[21025][1043];

String filename="/home/hadoop/srcData/B.txt";
final LineIterator it = FileUtils.lineIterator(new File(filename), "UTF-8");
try {
int i=-1;
//DecimalFormat df=new DecimalFormat("#.0000");
while (it.hasNext()) {
++i;
final String line = it.nextLine();
String[] ele=line.split("\t");
for(int j=0;j<ele.length;++j){
B[i][j]=Double.valueOf(ele[j]).doubleValue();//String -->double
//B[i][j]=Double.valueOf(df.format(B[i][j]) ).doubleValue();
}
}
} finally {
it.close();
}
//B
for (int i=0;i<B[0].length;++i)
for (int j=0;j<B.length;++j){
transformB[i][j]=B[j][i];
}

String fileName2="/home/hadoop/srcData/transB.txt";
BufferedWriter w2=new BufferedWriter(new FileWriter(fileName2));
for (int i=0;i<transformB.length;++i){
for (int j=0;j<transformB[i].length;++j)
{
w2.write(String.valueOf(transformB[i][j])+"\t");

}
if(i!=transformB.length-1)
w2.newLine();

}
w2.close();

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.LineIterator;

final LineIterator it = FileUtils.lineIterator(new File(""), "UTF-8");
try {
while (it.hasNext()) {
final String line = it.nextLine();
}
} finally {
it.close();
}

import java.io.IOException;
import java.io.FileWriter;
import  java.io.BufferedWriter;
String fileName2="/home/hadoop/srcData/transB.txt";
BufferedWriter w2=new BufferedWriter(new FileWriter(fileName2));
for (int i=0;i<transformB.length;++i){
for (int j=0;j<transformB[i].length;++j)
{
w2.write(String.valueOf(transformB[i][j])+"\t");

}
if(i!=transformB.length-1)
w2.newLine();//插入换行符

}
w2.close();