4. Collections (1)改写Student类，增加int grade属性。 (2)随机生成100个Student对象放入students数组。 (3)将students数组转换成studentList(List类型)。 (4)使用Collections.sort对student的成绩进行排序。 (5)使用Collections的min和max方法找到成绩最高的和成绩最低学生。 (6)使用Collections的binarySearch查找成绩等于60的学生。 (7)编写方法从studentList找出grade小于60的学生，放入otherList。 (8)使用List的removeAll方法，从studentList中移除otherList。 (9)使用Collections的shuffle方法，打乱studentList中学生排列的顺序。 (10)将studentList转换为数组。

1. 改写Student类，增加int grade属性。

public class Student {
    private String name;
    private int age;
    private int grade;

    public Student(String name, int age, int grade) {
        this.name = name;
        this.age = age;
        this.grade = grade;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public int getGrade() {
        return grade;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", grade=" + grade +
                '}';
    }
}

2. 随机生成100个Student对象放入students数组。

import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }
    }
}

3. 将students数组转换成studentList(List类型)。

import java.util.ArrayList;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }

        List<Student> studentList = new ArrayList<>();
        for (Student student : students) {
            studentList.add(student);
        }
    }
}

4. 使用Collections.sort对student的成绩进行排序。

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }

        List<Student> studentList = new ArrayList<>();
        for (Student student : students) {
            studentList.add(student);
        }

        Collections.sort(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade());
    }
}

5. 使用Collections的min和max方法找到成绩最高的和成绩最低学生。

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }

        List<Student> studentList = new ArrayList<>();
        for (Student student : students) {
            studentList.add(student);
        }

        Collections.sort(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade());

        System.out.println("最高成绩学生：" + Collections.max(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade()));
        System.out.println("最低成绩学生：" + Collections.min(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade()));
    }
}

6. 使用Collections的binarySearch查找成绩等于60的学生。

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }

        List<Student> studentList = new ArrayList<>();
        for (Student student : students) {
            studentList.add(student);
        }

        Collections.sort(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade());

        int index = Collections.binarySearch(studentList, new Student("", 0, 60), (s1, s2) -> s1.getGrade() - s2.getGrade());

        if (index >= 0) {
            System.out.println("成绩等于60的学生：" + studentList.get(index));
        } else {
            System.out.println("没有成绩等于60的学生");
        }
    }
}

7. 编写方法从studentList找出grade小于60的学生，放入otherList。

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }

        List<Student> studentList = new ArrayList<>();
        for (Student student : students) {
            studentList.add(student);
        }

        Collections.sort(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade());

        List<Student> otherList = new ArrayList<>();
        for (Student student : studentList) {
            if (student.getGrade() < 60) {
                otherList.add(student);
            }
        }
    }
}

8. 使用List的removeAll方法，从studentList中移除otherList。

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }

        List<Student> studentList = new ArrayList<>();
        for (Student student : students) {
            studentList.add(student);
        }

        Collections.sort(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade());

        List<Student> otherList = new ArrayList<>();
        for (Student student : studentList) {
            if (student.getGrade() < 60) {
                otherList.add(student);
            }
        }

        studentList.removeAll(otherList);
    }
}

9. 使用Collections的shuffle方法，打乱studentList中学生排列的顺序。

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }

        List<Student> studentList = new ArrayList<>();
        for (Student student : students) {
            studentList.add(student);
        }

        Collections.sort(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade());

        List<Student> otherList = new ArrayList<>();
        for (Student student : studentList) {
            if (student.getGrade() < 60) {
                otherList.add(student);
            }
        }

        studentList.removeAll(otherList);

        Collections.shuffle(studentList);
    }
}

10. 将studentList转换为数组。

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        Random random = new Random();
        Student[] students = new Student[100];
        for (int i = 0; i < students.length; i++) {
            students[i] = new Student("Student" + i, random.nextInt(10) + 15, random.nextInt(101));
        }

        List<Student> studentList = new ArrayList<>();
        for (Student student : students) {
            studentList.add(student);
        }

        Collections.sort(studentList, (s1, s2) -> s1.getGrade() - s2.getGrade());

        List<Student> otherList = new ArrayList<>();
        for (Student student : studentList) {
            if (student.getGrade() < 60) {
                otherList.add(student);
            }
        }

        studentList.removeAll(otherList);

        Collections.shuffle(studentList);

        Student[] studentArray = studentList.toArray(new Student[0]);
    }
}