java List接口的排序

谁借莪１个温暖的怀抱￠ 2022-05-27 02:42 183阅读 0赞

构造两个类，一个学生类，包含学号、姓名以及年龄，一个测试类，建立一个学生类的链表，然后按照学号由小到大排序，学号相同（纯属举例使用）按年龄排序。

要利用Collections类中的sort方法，并且需要重写其中的排序因子，其实就是一个匿名内部类，在这个匿名内部类中写出需要的排序规则。

package helloworld;
    
    public class Student {
    	String id;
    	String name;
    	int age;
    	
    	public Student(){}
    	public Student(String id, String name, int age){
    		this.id = id;
    		this.name = name;
    		this.age = age;
    	}
    	@Override
    	public String toString() {
    		return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
    	}
    	@Override
    	public int hashCode() {
    		final int prime = 31;
    		int result = 1;
    		result = prime * result + age;
    		result = prime * result + ((id == null) ? 0 : id.hashCode());
    		result = prime * result + ((name == null) ? 0 : name.hashCode());
    		return result;
    	}
    	@Override
    	public boolean equals(Object obj) {
    		if (this == obj)
    			return true;
    		if (obj == null)
    			return false;
    		if (getClass() != obj.getClass())
    			return false;
    		Student other = (Student) obj;
    		if (age != other.age)
    			return false;
    		if (id == null) {
    			if (other.id != null)
    				return false;
    		} else if (!id.equals(other.id))
    			return false;
    		if (name == null) {
    			if (other.name != null)
    				return false;
    		} else if (!name.equals(other.name))
    			return false;
    		return true;
    	}
    	
    }

package helloworld;
    
    import java.util.ArrayList;
    import java.util.Collections;
    import java.util.Comparator;
    import java.util.Iterator;
    import java.util.List;
    
    public class StudentTest {
    
    	public static void main(String[] args) {
    		List<Student> stu = new ArrayList<Student>();
    		Student stu1 = new Student("1000", "aaa", 18);
    		Student stu2 = new Student("1001", "bbb", 19);
    		Student stu3 = new Student("1002", "ccc", 18);
    		Student stu4 = new Student("1001", "ddd", 20);
    		
    		stu.add(stu1);
    		stu.add(stu2);
    		stu.add(stu3);
    		stu.add(stu4);
    		
    		Iterator<Student> it = stu.iterator();
    		while(it.hasNext()){
    			System.out.println(it.next());
    		}
    		Collections.sort(stu, new Comparator<Student>(){
    
    			@Override
    			public int compare(Student o1, Student o2) {
    				if(o1.id.compareTo(o2.id) == 0){
    					return o1.age-o2.age;
    				}
    				return o1.id.compareTo(o2.id);
    			}	
    		});
    		System.out.println("-----------");	
    		Iterator<Student> it1 = stu.iterator();
    		while(it1.hasNext()){
    			System.out.println(it1.next());
    		}
    		
    	}
    }