将每一位学生分成一块区域的占比。当系统随机到这个范围的某一个数字就代表是这个学生。
package com.lkbhua.Test2.test2; public class Student { private String name; private String gender; private int age; private double weight; public Student() {} public Student(String name, String gender, int age, double weight) { this.name = name; this.gender = gender; this.age = age; this.weight = weight; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public double getWeight() { return weight; } public void setWeight(double weight) { this.weight = weight; } @Override public String toString() { return "Student [name=" + name + ", gender=" + gender + ", age=" + age + ", weight=" + weight + "]"; } }package com.lkbhua.Test2.test2; import java.io.*; import java.util.ArrayList; import java.util.Arrays; public class test1 { public static void main(String[] args) throws IOException { // 1、把文件中所有的学生信息读取到内存中 ArrayList<Student> list = new ArrayList<>(); // 2、创建IO流 BufferedReader br = new BufferedReader(new FileReader("lkb04-File&IOCode\\a.txt")); String line; while((line = br.readLine()) != null) { // 3、把文件中的数据封装成对象 String[] arr = line.split("-"); Student s = new Student(arr[0], arr[1], Integer.parseInt(arr[2]), Double.parseDouble(arr[3])); list.add(s); } br.close(); //System.out.println("所有学生信息:"); //System.out.println(list); // 2、计算权重的总和 double weight = 0; for (Student stu : list) { weight = weight + stu.getWeight(); } //System.out.println("权重的总和:"); //System.out.println(weight); // 3、计算每一个人的实际占比 // 1/10 = 0.1 然后把结果存起来 double[] arr = new double[list.size()]; int index = 0; for (Student stu : list) { arr[index] = stu.getWeight() / weight; index++; } //System.out.println("每个人的实际占比:"); //System.out.println(Arrays.toString(arr)); // 4、把每一个学生的占比范围都计算出来 // [0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1] // [0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0] for (int i = 1; i < arr.length; i++) { arr[i] = arr[i] + arr[i - 1]; } //System.out.println("每个人的占比范围:"); //System.out.println(Arrays.toString(arr)); // 5、生成随机数，判断随机数属于哪个区间 // 获取一个0.0 - 1.0之间的随机数 double number = Math.random(); //System.out.println("随机数:"); //System.out.println(random); // 6、遍历数组，判断随机数属于哪个区间 // 二分查找法 // 方法返回值: -插入点 - 1 int index2 = Arrays.binarySearch(arr, number); // 获取number在数组中的插入点位置 // 插入点 = -结果 - 1 （运算知识） int result = -index2 - 1; //System.out.println("随机数属于哪个区间:"); //System.out.println(result); Student stu = list.get(result); System.out.println("中奖学生信息:"); System.out.println(stu); // 7、修改学生的权重 double w = stu.getWeight() / 2; stu.setWeight(w); // 8、把修改后的数据写入文件 BufferedWriter bw = new BufferedWriter(new FileWriter("lkb04-File&IOCode\\a.txt")); for (Student stu2 : list) { bw.write(stu2.getName() + "-" + stu2.getGender() + "-" + stu2.getAge() + "-" + stu2.getWeight()); bw.newLine(); } bw.close(); System.out.println("修改后的数据写入文件成功"); } }
