package com.swift; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; import java.util.Scanner; public class Test2_ObjectIO { @SuppressWarnings("unchecked") public static void main(String[] args) { /* * 第2题: 有五个学生,每个学生有3门课(语文、数学、英语)的成绩,写一个程序接收从键盘输入学生的信息, * 输入格式为:name,30,30,30(姓名,三门课成绩),然后把输入的学生信息按总分从高到低的顺序写入到一个名称"stu.txt"文件中。 * 要求:stu.txt文件的格式要比较直观,打开这个文件,就可以很清楚的看到学生的信息。 */ List<Student> list = new ArrayList<Student>(); Scanner scan = new Scanner(System.in); for (int i = 1; i <=5; i++) { System.out.println("请输入第"+i+"学生信息:格式为 name 60 60 60"); String name = scan.next(); Float yuwen = scan.nextFloat(); Float shuxue = scan.nextFloat(); Float yingyu = scan.nextFloat(); Student stu = new Student(name, yuwen, shuxue, yingyu); list.add(stu); } for(Student stu:list) { System.out.println(stu.toString()); } Collections.sort(list, new Comparator<Student>() { @Override public int compare(Student o1, Student o2) { float num=(o2.getShuxue()+o2.getYingyu()+o2.getYuwen())-(o1.getShuxue()+o1.getYingyu()+o1.getYuwen()); int i=(int) num; return i; } }); for(Student stu:list) { System.out.println(stu.toString()); } } } class Student { private String name; private float yuwen; private float shuxue; private float yingyu; public String getName() { return name; } public void setName(String name) { this.name = name; } public float getYuwen() { return yuwen; } public void setYuwen(float yuwen) { this.yuwen = yuwen; } public float getShuxue() { return shuxue; } public void setShuxue(float shuxue) { this.shuxue = shuxue; } public float getYingyu() { return yingyu; } public void setYingyu(float yingyu) { this.yingyu = yingyu; } public Student(String name, float yuwen, float shuxue, float yingyu) { super(); this.name = name; this.yuwen = yuwen; this.shuxue = shuxue; this.yingyu = yingyu; } public Student() { super(); } @Override public String toString() { return "Student [name=" + name + ", yuwen=" + yuwen + ", shuxue=" + shuxue + ", yingyu=" + yingyu + "]"; } }
比较器就是个匿名内部类,Collections.sort(list,Comparator<Student>(){});
然后实现其中的compare方法,返回一个int类型的值,正数 负数 0分别代表大于小于等于
增加IO流的内容代码如下;
package com.swift; import java.io.BufferedWriter; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStreamWriter; import java.io.UnsupportedEncodingException; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; import java.util.Scanner; public class Test2_ObjectIO { @SuppressWarnings("unchecked") public static void main(String[] args) { /* * 第2题: 有五个学生,每个学生有3门课(语文、数学、英语)的成绩,写一个程序接收从键盘输入学生的信息, * 输入格式为:name,30,30,30(姓名,三门课成绩),然后把输入的学生信息按总分从高到低的顺序写入到一个名称"stu.txt"文件中。 * 要求:stu.txt文件的格式要比较直观,打开这个文件,就可以很清楚的看到学生的信息。 */ List<Student> list = initiateList(); for(Student stu:list) { System.out.println(stu.toString()); } Collections.sort(list, new Comparator<Student>() { @Override public int compare(Student o1, Student o2) { float num=(o2.getShuxue()+o2.getYingyu()+o2.getYuwen())-(o1.getShuxue()+o1.getYingyu()+o1.getYuwen()); int i=(int) num; return i; } }); initiate_IO(list); } private static void initiate_IO(List<Student> list) { BufferedWriter bw; StringBuffer sb=new StringBuffer(); for(Student stu:list) { sb.append(stu.toString()); sb.append("\r\n"); } try { bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("src\\stu.txt"),"utf-8"));//需要标明路径 bw.write(sb.toString()); bw.flush(); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } private static List<Student> initiateList() { List<Student> list = new ArrayList<Student>(); Scanner scan = new Scanner(System.in); for (int i = 1; i <=5; i++) { System.out.println("请输入第"+i+"学生信息:格式为 name 60 60 60"); String name = scan.next(); Float yuwen = scan.nextFloat(); Float shuxue = scan.nextFloat(); Float yingyu = scan.nextFloat(); Student stu = new Student(name, yuwen, shuxue, yingyu); list.add(stu); } return list; } } class Student { private String name; private float yuwen; private float shuxue; private float yingyu; public String getName() { return name; } public void setName(String name) { this.name = name; } public float getYuwen() { return yuwen; } public void setYuwen(float yuwen) { this.yuwen = yuwen; } public float getShuxue() { return shuxue; } public void setShuxue(float shuxue) { this.shuxue = shuxue; } public float getYingyu() { return yingyu; } public void setYingyu(float yingyu) { this.yingyu = yingyu; } public Student(String name, float yuwen, float shuxue, float yingyu) { super(); this.name = name; this.yuwen = yuwen; this.shuxue = shuxue; this.yingyu = yingyu; } public Student() { super(); } @Override public String toString() { return "Student [name=" + name + ", yuwen=" + yuwen + ", shuxue=" + shuxue + ", yingyu=" + yingyu + "]"; } }
原文地址:https://www.cnblogs.com/qingyundian/p/8280078.html
时间: 2024-10-13 13:37:57