180217_java learn to store classes with multiple strings in _treeset and set collations

There is the person class as follows:

1 class Person {2String name; 3 int Age ; 4 String address; 5 } 　　 　　 　　

There are main as follows:

1 ImportJava.util.TreeSet;2 3  Public classtest{4  　　  Public Static voidMain (string[] args) {5person P1 =NewPerson ("AA", "CN");6person P2 =NewPerson ("BB", "JP");7Person P3 =NewPerson ("CC", +, "CN");8 9treeset<person> persons =NewTreeset<>();Ten Persons.add (p1); One Persons.add (p2); A Persons.add (p3); -  　　　　  for(Object person:persons) { - System.out.println (person); the } - } -}

Because TreeSet is a sortable collection, you specify a collation for the holding object (person).

Collation: ASC (Ascending), age > Address > Name
So rewrite the person's CompareTo ():

1  Public intcompareTo (Person o) {2     if( This. Age >o.age) {3         return1;4}Else if( This. Age <o.age) {5         return-1;6     }7     //judge The age who is big, if equal, then judge the address8     intx = This. Address.compareto (o.address);9     if(x! = 0){Ten         returnx; One     } A     //judge the address who is big, if equal, then judge the name -     return  This. Name.compareto (o.name); -}

Note: to sort desc:

1, the age comparison in exchange 1/-1;
2. Return the opposite value in address comparison;
3, the name comparison to return the opposite value;

The logical order of the above code:
The incoming comparison object o is compared with itself;
If This.age > O.age, return "1";
If This.age < O.age, return "-1";
If equal, compare address;
Make x = This.address.compareTo (o.address);
if x! = 0, which is not equal, X is the value to return (1/-1);
if x = = 0, i.e. equal, compare name;
The value of This.name.compareTo (O.name) is the value to be returned:
If the value is 1, that is greater than,
If the value is-1, which is less than,
If the value is 0, that is equal to all three, it is exactly equal and should not be deposited.

Full code:

1  PackageTobky;2 3 ImportJava.util.TreeSet;4 5  Public classtest{6      Public Static voidMain (string[] args) {7person P1 =NewPerson ("AA", "CN");8person P2 =NewPerson ("BB", "JP");9Person P3 =NewPerson ("CC", +, "CN");Ten  Onetreeset<person> persons =NewTreeset<>(); A Persons.add (p1); - Persons.add (p2); - Persons.add (p3); the  -          for(Object person:persons) { - System.out.println (person); -         } +         //use for each less than iterator code -  +     } A } at  - classPersonImplementsComparable<person>{ - String name; -     intAge ; - String address; -  in      PublicPerson (String name,intAge , String address) { -          This. Name =name; to          This. Age =Age ; +          This. Address =address; -     } the  * @Override $      PublicString toString () {Panax Notoginseng         return"Person{" + -"Name=" + name + ' \ ' + the", age=" + Age + +", address= ' + address + ' \ ' + A‘}‘; the  　　 } +  -  　　 @Override $  　　  Public intcompareTo (Person o) { $  　　　　 if( This. Age >o.age) { -  　　　　　　 return1; -}Else if( This. Age <o.age) { the  　　　　　　 return-1; -  　　　　 }Wuyi  　　　　 //judge The age who is big, if equal, then judge the address the  　　　　 intx = This. Address.compareto (o.address); -  　　　　 if(x! = 0){ Wu  　　　　　　 returnx; -  　　　　 } About  　　　　 //judge the address who is big, if equal, then judge the name $  　　　　 return  This. Name.compareto (o.name); - 　　 } -}

180217_java learn to store classes with multiple strings in _treeset and set collations