JAVA8--List.stream().collect

分手后的思念是犯贱 2023-02-21 12:45 26阅读 0赞

package mypack;
    
    import java.text.ParseException;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    import java.util.stream.Collectors;
    
    
    public class Test
    {
    	public static void main(String[] args) throws ParseException
    	{
    		Student s1 = new Student("1", "S1", 10);
    		Student s2 = new Student("1", "S1", 10);
    		Student s3 = new Student("1", "S1", 10);
    		Student s4 = new Student("2", "S2", 20);
    		Student s5 = new Student("2", "S2", 20);
    		Student s6 = new Student("2", "S2", 20);
    		Student s7 = new Student("3", "S3", 30);
    		Student s8 = new Student("3", "S3", 30);
    		Student s9 = new Student("4", "S4", 40);
    		Student s10 = new Student("4", "S4", 40);
    		
    		List<Student> sList = new ArrayList<Student>();
    		sList.add(s1);
    		sList.add(s2);
    		sList.add(s3);
    		sList.add(s4);
    		sList.add(s5);
    		sList.add(s6);
    		sList.add(s7);
    		sList.add(s8);
    		sList.add(s9);
    		sList.add(s10);
    		
    		Map<ParentStudent, List<Student>> sMap = sList.stream().collect(Collectors.groupingBy(student -> new ParentStudent(student.getId())));
    		
    		sMap.forEach((key, value) -> {
                System.out.print("id:" + key.getId() + "====");
                for(Student s : value)
                {
                	System.out.print("name:" + s.getName() + ",");
                }
                System.out.println("");
            });
    	}
    
    }
    
    class ParentStudent extends SupperStudent
    {
    	String id;
    	
    	public ParentStudent(String sid)
    	{
    		this.id = sid;
    	}
    	
    	@Override
    	public int hashCode()
    	{
    		final int prime = 31;
    		int result = 1;
    		result = prime * result + ((id == null) ? 0 : id.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;
    		ParentStudent other = (ParentStudent)obj;
    		if(id == null)
    		{
    			if(other.id != null)
    				return false;
    		}
    		else if(!id.equals(other.id))
    			return false;
    		return true;
    	}
    
    	public String getId()
    	{
    		return id;
    	}
    
    	public void setId(String id)
    	{
    		this.id = id;
    	}
    
    }
    
    class SupperStudent
    {
    	private String sex;
    
    	public String getSex()
    	{
    		return sex;
    	}
    
    	public void setSex(String sex)
    	{
    		this.sex = sex;
    	}
    	
    }
    
    class Student
    {
    	String id;
    	String name;
    	int age;
    	
    	public Student(String sid)
    	{
    		this.id = sid;
    	}
    	
    	public Student(String sid, String sname, int sage)
    	{
    		this.id = sid;
    		this.name = sname;
    		this.age = sage;
    	}
    
    	public String getId()
    	{
    		return id;
    	}
    
    	public void setId(String id)
    	{
    		this.id = id;
    	}
    
    	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;
    	}
    
    }