Java 里Collections的min和max方法

我不是女神ヾ 2023-08-17 15:57 130阅读 0赞

## 方法一 ##

此方法需要传入一个实现了Comparable接口的对象类的集合

创建实现了Comparable的对象类

public class Student1 implements Comparable<Student1> { 
     
        private String name;
        private int age;
     
        public Student1() { 
        }
     
        public Student1(String name, int age) { 
            this.name = name;
            this.age = age;
        }
     
        public String getName() { 
            return name;
        }
     
        public void setName(String name) { 
            this.name = name;
        }
     
        public Integer getAge() { 
            return age;
        }
     
        public void setAge(Integer age) { 
            this.age = age;
        }
     
        @Override
        public int compareTo(Student1 s) { 
            int num = this.age - s.age;
            int num1 = (num == 0 ? this.name.compareTo(s.name) : num);
            return num1;
        }
    }

调用

import java.util.ArrayList;
    import java.util.Collections;
    import java.util.List;
     
    public class Student1Test { 
        public static void main(String[] args) { 
            List<Student1> list1 = new ArrayList<Student1>();
            list1.add(new Student1("林青霞", 27));
            list1.add(new Student1("风清扬", 30));
            list1.add(new Student1("刘晓曲", 28));
            list1.add(new Student1("武鑫", 29));
            list1.add(new Student1("林青霞", 27));
     
            Student1 min=Collections.min(list1);
            System.out.println(min.getName()+"---"+min.getAge());
            Student1 max=Collections.max(list1);
            System.out.println(max.getName()+"---"+max.getAge());
        }
    }

## 方法二 ##

此方法传入一个对象类的集合，以及一个比较器  
（`根据比较器定义的规则来对对象类的集合做大小比较`）

创建对象类

public class Student2 { 
     
        private String name;
        private int age;
     
        public Student2() { 
        }
     
        public Student2(String name, int age) { 
            this.name = name;
            this.age = age;
        }
     
        public String getName() { 
            return name;
        }
     
        public void setName(String name) { 
            this.name = name;
        }
     
        public Integer getAge() { 
            return age;
        }
     
        public void setAge(Integer age) { 
            this.age = age;
        }
    }

调用

import java.util.ArrayList;
    import java.util.Collections;
    import java.util.Comparator;
    import java.util.List;
     
    public class Student2Test { 
        public static void main(String[] args) { 
            List<Student2> list2 = new ArrayList<Student2>();
            list2.add(new Student2("林青霞", 27));
            list2.add(new Student2("风清扬", 30));
            list2.add(new Student2("刘晓曲", 28));
            list2.add(new Student2("武鑫", 29));
            list2.add(new Student2("林青霞", 27));
          
            Student2 min=Collections.min(list2,new MyComparator());
            System.out.println(min.getName()+"---"+min.getAge());
            Student2 max=Collections.max(list2,new MyComparator());
            System.out.println(max.getName()+"---"+max.getAge());
        }
    }
     
    class MyComparator implements Comparator<Student2> { 
        @Override
        public int compare(Student2 s1, Student2 s2) { 
            int num = s1.getAge() - s2.getAge();
            int num1 = (num == 0 ? s1.getName().compareTo(s2.getName()) : num);
            return num1;
        }
    }

本文转载自：https://blog.csdn.net/lei2879223426/article/details/77430206