Java List获取集合中的最大值或最小值

电玩女神 2022-09-07 09:55 311阅读 0赞

1.List集合中的元素为基本类型，我们可以使用java.util中的Collections提供的方法，来取出最大值或者最小值。  
（1）Integer类型

package com.yuxuange.study.test;
    
    import java.util.*;
    
    public class Test { 
    
        public static void main(String[] args) { 
            List<Integer> list = new LinkedList<>();
            list.add(99);
            list.add(54);
            list.add(82);
            list.add(12);
            list.add(33);
            list.add(79);
            list.add(90);
            list.add(7);
            list.add(66);
            list.add(38);
            list.add(7);
            System.out.println(list.toString());
            Integer max = Collections.max(list);
            System.out.println("集合中最大值为：" + max);
            Integer min = Collections.min(list);
            System.out.println("集合中最小值为：" + min);
        }
    }

输出的结果为：  
![整型输出结果][32a1d452916644129bc2cc9bb4d79834.png_pic_center]  
（2）Double类型

package com.yuxuange.study.test;
    
    import java.util.*;
    
    public class Test { 
    
        public static void main(String[] args) { 
            List<Double> list = new LinkedList<>();
            list.add(97.42);
            list.add(83.555);
            list.add(99.8045);
            list.add(45.33);
            list.add(8.2006);
            list.add(54.333);
            list.add(72.9055);
            list.add(56.999997);
            list.add(20.9);
            list.add(6.099912);
            System.out.println(list.toString());
            Double max = Collections.max(list);
            System.out.println("集合中最大值为：" + max);
            Double min = Collections.min(list);
            System.out.println("集合中最小值为：" + min);
        }
    }

输出结果为：  
![Double类型输出结果][Double]  
2.List集合中的元素为引用类型时  
（1）String类型

package com.yuxuange.study.test;
    
    import java.util.*;
    
    public class Test { 
    
        public static void main(String[] args) { 
            List<String> list = new LinkedList<>();
            list.add("97.435");
            list.add("92");
            list.add("80.3455");
            list.add("10.9833");
            list.add("52");
            list.add("35.663444");
            list.add("79.0");
            list.add("42");
            list.add("83.482");
            list.add("26.454448");
            System.out.println(list.toString());
            String max = Collections.max(list);
            System.out.println("集合中最大值为：" + max);
            String min = Collections.min(list);
            System.out.println("集合中最小值为：" + min);
        }
    }

![String类型输出结果][String]

（2）对象，比如有个对象集合，集合中保存了学生的对象信息，我们要根据学号，年龄等字段找出对应的最大值或者最小值

package com.yuxuange.study.test;
    
    import java.util.*;
    
    public class Test { 
    
        public static void main(String[] args) { 
            List<Student> list = new LinkedList<>();
            Student zhangsan = new Student(99, "张三", 28, 96.0);
            Student lisi = new Student(82, "李四", 25, 89.0);
            Student wangwu = new Student(26, "王五", 23, 72.5);
            Student zhaoliu = new Student(68, "赵六", 30, 65.5);
            Student tianqi = new Student(8, "田七", 26, 100.0);
            Student fengba = new Student(47, "冯八", 21, 52.5);
            Student jinjiu = new Student(14, "金九", 27, 46.5);
            list.add(zhangsan);
            list.add(lisi);
            list.add(wangwu);
            list.add(zhaoliu);
            list.add(tianqi);
            list.add(fengba);
            list.add(jinjiu);
            System.out.println(list.toString());
            Student noMax = list.stream().max(Comparator.comparing(Student::getNo)).get();
            Student noMin = list.stream().min(Comparator.comparing(Student::getNo)).get();
            System.out.println("集合中学号最大的学生信息为" + noMax);
            System.out.println("集合中学号最小的学生信息为" + noMin);
            Student ageMax = list.stream().max(Comparator.comparing(Student::getAge)).get();
            Student ageMin = list.stream().min(Comparator.comparing(Student::getAge)).get();
            System.out.println("集合中年龄最大的学生信息为" + ageMax);
            System.out.println("集合中年龄最小的学生信息为" + ageMin);
        }
    }
    
    class Student { 
    
        private Integer no;
    
        private String name;
    
        private Integer age;
    
        private Double score;
    
        public Student(Integer no, String name, Integer age, Double score) { 
            this.no = no;
            this.name = name;
            this.age = age;
            this.score = score;
        }
    
        public Integer getNo() { 
            return no;
        }
    
        public void setNo(Integer no) { 
            this.no = no;
        }
    
        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;
        }
    
        public Double getScore() { 
            return score;
        }
    
        public void setScore(Double score) { 
            this.score = score;
        }
    
        @Override
        public String toString() { 
            return "Student{" +
                    "no=" + no +
                    ", name='" + name + '\'' +
                    ", age=" + age +
                    ", score=" + score +
                    '}';
        }
    }

输出结果为：  
![对象类型输出结果][8cd7afcc31be4b919b2ab2c040620aa4.png_pic_center]

[32a1d452916644129bc2cc9bb4d79834.png_pic_center]: /images/20220829/c7685cd079984d7e9b4d9cee214fe509.png
[Double]: /images/20220829/08d672b10f1e4b83a0cb5296f9f403d9.png
[String]: /images/20220829/f61f131847684e80820dabefe99a0e73.png
[8cd7afcc31be4b919b2ab2c040620aa4.png_pic_center]: /images/20220829/d2a95af0c7664ea79856f70ad7c581c6.png