java IO 字节读写操作的疑问

Java code:

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

public class TestIO {
public static void main(String[] args) {
String fileName="E://test.txt";
String otherFileName="E://target.text";
testOutputStream(fileName, otherFileName);
testInputStream(fileName);
}

public static void testInputStream(String fileName){
File file=new File(fileName);
try {
InputStream is=new FileInputStream(file);
int temp;
while((temp=is.read())!=-1){
System.out.print((char)temp);
}

} catch (Exception e) {
e.printStackTrace();
}
}

public static void testOutputStream(String fileName,String otherFileName){
File source=new File(fileName);
File target=new File(otherFileName);
try {
InputStream is=new FileInputStream(source);
OutputStream os=new FileOutputStream(target);

int b;
while((b=is.read())!=-1){
os.write(b);
}
} catch (Exception e) {
e.printStackTrace();
}