一笔试小题---文件读写操作（希望对刚毕业找工作的朋友有所帮助）

datuo 写道

自己把文本里面一行的东西定义个对象。实现Comparable接口

class Student implements Comparable
{
 int age;
 String name;

 public Student(int age, String name)
 {
  this.age  = age;
  this.name = name;
 }
 public int compareTo(Object o)
 {
  Student s = (Student)o;
  return age > s.age ? 1:(age == s.age ? 0 : -1);
 }
}

class Student implements Comparable
{
int age;
String name;
public Student(int age, String name)
{
this.age  = age;
this.name = name;
}
public int compareTo(Object o)
{
Student s = (Student)o;
return age > s.age ? 1:(age == s.age ? 0 : -1);
}
}

随便你用什么排序都行了。还可以扩展到多个属性。

 

 这种思路是很好的，也能很好解决后面数字重复的问题。而且这种完全用了面向对象的思想。

 代码如下：student.java封装文件中的对象， Test.java为测试类

public class Student implements Comparable<Student> {
    private String name;
    private int orderNumber;

    public Student() {

    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getOrderNumber() {
        return orderNumber;
    }

    public void setOrderNumber(int orderNumber) {
        this.orderNumber = orderNumber;
    }

    public int compareTo(Student o) {
        // return this.orderNumber>o.orderNumber?1:(this.orderNumber==o.orderNumber?0:-1);//小到大排序
    return o.orderNumber > this.orderNumber ? 1
                : (o.orderNumber == this.orderNumber ? 0 : -1);// 大到小排序

    }
}

public class Student implements Comparable<Student> {
private String name;
private int orderNumber;
public Student() {
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getOrderNumber() {
return orderNumber;
}
public void setOrderNumber(int orderNumber) {
this.orderNumber = orderNumber;
}
public int compareTo(Student o) {
// return this.orderNumber>o.orderNumber?1:(this.orderNumber==o.orderNumber?0:-1);//小到大排序
return o.orderNumber > this.orderNumber ? 1
: (o.orderNumber == this.orderNumber ? 0 : -1);// 大到小排序
}
}

 

Test.java

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test {
    public static void main(String[] ars){
        Test test = new Test();
        test.sortFile("d:/source.txt", "d:/dest.txt");
    }

    public void sortFile(String sourceFile, String destFile) {
        BufferedReader bReader = null;
        PrintWriter pWriter = null;
        try {
            bReader = new BufferedReader(new InputStreamReader(
                    new FileInputStream(sourceFile)));
            String keyString = bReader.readLine();
            List<Student> list = new ArrayList<Student>();
            while (keyString != null) {
                String[] ar = keyString.split(" ");
                Student student = new Student();
                student.setName(ar[0]);
                student.setOrderNumber(Integer.parseInt(ar[1]));
                list.add(student);
                keyString = bReader.readLine();
            }
            System.out.println("读取文件成功...");
            Object[] objects = list.toArray();
            Arrays.sort(objects);
            pWriter = new PrintWriter(new FileOutputStream(destFile));
            for (Object o:objects) {
                Student student = (Student) o;
                pWriter.println(new StringBuilder(student.getName())
                        .append(" ").append(student.getOrderNumber())
                        .toString());
            }
            pWriter.flush();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (bReader != null) {
                try {
                    bReader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (pWriter != null) {
                pWriter.close();
            }
        }
        System.out.println("保存文件成功....");
    }
}