1、将字符串「a-b-c-d-e-f」按 「-」 切割，找到 「c」字符，替换为大写，然后倒序输出 「f-e-d-C-b-a」。

public class Test1 {
	public static void main(String[] args) {
		String s1 = "a-b-c-d-e-f";
		String[] s2 = s1.split("-");
		for(String s3:s2) {
			System.out.println(s3);
		}
		
		String s4 = "";
		for(int i = 0;i<s2.length;i++) {
			s4 += s2[i] +"-";
			
		}
		
		String s5 = s4.substring(0,s4.length()-1);
		s5 = s5.replace("c", "C");
		System.out.println(new StringBuffer(s5).reverse().toString());
	}
}

2、定义学生类（包含学号、姓名、年龄），将你所在小组组员添加到一个集合中，并按学号排序后输出。

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

	public int getCode() {
		return code;
	}

	public void setCode(int code) {
		this.code = code;
	}

	public String getName() {
		return name;
	}

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

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

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

	@Override
	public int compareTo(Student o) {
		int flag;
		if (this.code > o.code) {
			flag = -1;
		} else if (this.code == o.code) {
			flag = 0;
		} else {
			flag = 1;
		}
		return flag;
	}

	@Override
	public String toString() {
		return "Student [code=" + code + ", name=" + name + ", age=" + age
				+ "]";
	}
}

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


public class Test2 {
	public static void main(String[] args) {
		List<Student> teams = new ArrayList<Student>();
		// 新建学生对象
		Student stu1 = new Student(1, "陆洋", 24);
		Student stu2 = new Student(3, "顾锐", 19);
		Student stu3 = new Student(2, "关凌", 24);
		Student stu4 = new Student(4, "钱佳雷", 25);
		// 向集合添加学生对象
		teams.add(stu1);
		teams.add(stu2);
		teams.add(stu3);
		teams.add(stu4);
		// 按学号倒叙排列
		Collections.sort(teams);
		// 遍历学生
		for (Student stu : teams) {
			System.out.println(stu);
		}
	}
}

import java.util.List;

public class Service {
	private static Service service = new Service();
	
	private Service() {
		
	}
	
	public static Service getInstance() {
		return service;
	}
	
	public Student randomStu(List<Student> stus) {
		if (null != stus && !stus.isEmpty()) {
			return stus.get((int)(Math.random() * stus.size()));
		} else {
			return null;
		}
	}
}

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

public class Test3 {
	public static void main(String[] args) {
		List<Student> teams = new ArrayList<Student>();
		Student stu1 = new Student(1, "陆洋", 24);
		Student stu2 = new Student(3, "顾锐", 19);
		Student stu3 = new Student(2, "关凌", 24);
		Student stu4 = new Student(4, "钱佳雷", 25);
		teams.add(stu1);
		teams.add(stu2);
		teams.add(stu3);
		teams.add(stu4);

		// 通过静态方法获取对象
		Service service = Service.getInstance();

		System.out.println("==========随机抽取学生=============");
		Student randomStu = service.randomStu(teams);
		System.out.println(randomStu);
	}
}