Java:1.HashSet的遍历；2.TreeSet的两种排序方式;3.字符串中每个字符出现的次数统计；4.斗地主的洗牌、发牌以及排序的实现。

1.HashSet的遍历

Student类：
public class Student {
private String name;
private int age;

public Student() {
}

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

public String getName() {
    return name;
}

public int getAge() {
    return age;
}

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

}
HashSetTest类：

import java.util.HashSet;

public class HashSetTest {
    public static void main(String[] args) {
        HashSet<Student> hashSet = new HashSet<>();
        Student student1 = new Student("张三", 20);
        Student student2 = new Student("李四", 21);
        Student student3 = new Student("王五", 22);
        hashSet.add(student1);
        hashSet.add(student2);
        hashSet.add(student3);
        for (Student student : hashSet) {
            System.out.println(student.getName() + "---" + student.getAge());
        }
    }
}

运行结果为：

2.TreeSet的两种排序方式

（1）自然排序：
Student类：

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

    public Student() {
    }

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

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

    @Override
    public int compareTo(Student o) {
        int num1 = this.getAge() - o.getAge();
        int num2 = (num1 == 0) ? (this.getName().compareTo(o.getName())) : num1;
        return num2;
    }
}

TreeSetTest类：

import java.util.TreeSet;

public class TreeSetTest {
    public static void main(String[] args) {
        TreeSet<Student> treeSet = new TreeSet<>();
        Student student1 = new Student("张三", 20);
        Student student2 = new Student("张三", 22);
        Student student3 = new Student("李四", 21);
        Student student4 = new Student("王五", 22);
        treeSet.add(student1);
        treeSet.add(student2);
        treeSet.add(student3);
        treeSet.add(student4);
        for (Student student : treeSet) {
            System.out.println(student.getName() + "---" + student.getAge());
        }
    }
}

运行结果为：

（2）比较器排序
Student类：

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

    public Student() {
    }

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

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

TreeSetTest类：

import java.util.Comparator;
import java.util.TreeSet;

public class TreeSetTest {
    public static void main(String[] args) {
        TreeSet<Student> treeSet = new TreeSet<>(
                new Comparator<Student>() {
                    @Override
                    public int compare(Student s1, Student s2) {
                        int num1 = s1.getName().compareTo(s2.getName());
                        int num2 = num1 == 0 ? (s1.getAge() - s2.getAge()) : num1;
                        return num2;
                    }
                });
        Student student1 = new Student("张三", 20);
        Student student2 = new Student("张三", 22);
        Student student3 = new Student("李四", 21);
        Student student4 = new Student("王五", 22);
        treeSet.add(student1);
        treeSet.add(student2);
        treeSet.add(student3);
        treeSet.add(student4);
        for (Student student : treeSet) {
            System.out.println(student.getName() + "---" + student.getAge());
        }
    }
}

运行结果为：

3.字符串中每个字符出现的次数统计

import java.util.HashMap;

public class CharCount {
    public static void main(String[] args) {
        String str = "aababcabcdabcde";
        HashMap<Character, Integer> hashMap = new HashMap<>();
        char[] arr = str.toCharArray();
        for (char c : arr) {
            if (hashMap.containsKey(c)) {
                Integer integer = hashMap.get(c);
                hashMap.put(c, integer + 1);
            } else {
                hashMap.put(c, 1);
            }
        }
        System.out.println(hashMap);
    }
}

运行结果为：

4.斗地主的洗牌、发牌以及排序的实现

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.TreeSet;

public class Poker {
    public static void main(String[] args) {

        String[] color = {"♥", "♠", "♣", "♦"};
        String[] num = {"A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"};
        HashMap<Integer, String> hm = new HashMap<>();
        ArrayList<Integer> list = new ArrayList<>();
        int index = 0;
        for (String s1 : num) {
            for (String s2 : color) {
                hm.put(index++, s2.concat(s1));
            }
        }
        hm.put(++index, "☀");
        hm.put(++index, "");
        list.addAll(hm.keySet());
        Collections.shuffle(list);
        TreeSet<Integer> gaijin = new TreeSet<>();
        TreeSet<Integer> daozai = new TreeSet<>();
        TreeSet<Integer> xingzai = new TreeSet<>();
        TreeSet<Integer> dipai = new TreeSet<>();
        for (int i = 0; i < list.size(); i++) {
            if (i >= list.size() - 3) {
                dipai.add(list.get(i));
            } else if (i % 3 == 0) {
                gaijin.add(list.get(i));
            } else if (i % 3 == 1) {
                daozai.add(list.get(i));
            } else {
                xingzai.add(list.get(i));
            }
        }
        lookPoker(hm, gaijin, "高进");
        lookPoker(hm, daozai, "刀仔");
        lookPoker(hm, xingzai, "星仔");
        lookPoker(hm, dipai, "底牌");
    }

    public static void lookPoker(HashMap<Integer, String> hm, TreeSet<Integer> ts, String name) {
        System.out.println(name + ":\t");
        for (Integer t : ts) {
            System.out.print(hm.get(t));
        }
        System.out.println();
    }
}

运行结果为：