新建 文本文档 (3).txt

输入5个学生的成绩（从0到100的整数）

import java.io.BufferedWriter; 
import java.io.FileWriter; 
import java.io.IOException; 
import java.util.Scanner; 

public class Save { 

public static void main(String[] args) { 
for (int i = 0; i < 5; i++) { 
String str = ""; 
Scanner scan = new Scanner(System.in); 
try { 
BufferedWriter buf = new BufferedWriter(new FileWriter( 
"data.txt", true)); 
str = scan.nextLine(); 
buf.write(str); 
buf.newLine(); 
buf.flush(); 
} catch (IOException e) { 
e.printStackTrace(); 
} 
} 
} 
} 
================================ 
import java.io.BufferedReader; 
import java.io.FileNotFoundException; 
import java.io.FileReader; 
import java.io.IOException; 
import java.util.ArrayList; 
import java.util.Collections; 

public class Read { 

public static void main(String[] args) { 
try { 
double sum = 0; 
BufferedReader buf = new BufferedReader(new FileReader("data.txt")); 
ArrayList<Double> list = new ArrayList<Double>(); 
String str = ""; 
while ((str = buf.readLine()) != null) { 
list.add(Double.parseDouble(str)); 
} 
for (int i = 0; i < list.size(); i++) { 
sum = sum + list.get(i); 
} 
System.out.println("arr is " + sum / list.size()); 
Collections.sort(list); 
for (int i = 0; i < list.size(); i++) { 
System.out.println(list.get(i)); 
} 
} catch (FileNotFoundException e) { 
e.printStackTrace(); 
} catch (IOException e) { 
e.printStackTrace(); 
} 
} 
}