java - How can I sort an ArrayList of objects? -


i have , arraylist 2 strings , integer, need sort string name , string lastname, tried method collections.sort this

    collections.sort(myarraylist, (contact v1, contact v2) -> v1.getname().compareto(v2.getname()));

but sorts arraylist names, , doesn't include last name, how can add sort last names?

well need change comparison function include other fields this

    collections.sort(contacts, (contact c1, contact c2) -> {         int firstnamecomparisonresult = c1.getfirstname().compareto(c2.getfirstname());         if (firstnamecomparisonresult != 0) {             return firstnamecomparisonresult;         } else {             return c1.getlastname().compareto(c2.getlastname());         }     });

warning: assumes there no nulls.

full code used if want take look:

class contact{     final string firstname;     final string lastname;     final int age;      public string getfirstname() {         return firstname;     }      public string getlastname() {         return lastname;     }      public int getage() {         return age;     }      public contact(string firstname, string lastname, int age) {         this.firstname = firstname;         this.lastname = lastname;         this.age = age;     }      @override     public string tostring() {         return "contact{" +                 "firstname='" + firstname + '\'' +                 ", lastname='" + lastname + '\'' +                 ", age=" + age +                 '}';     } }  @test public void sorttest(){     list<contact> contacts = new arraylist<>();     contacts.add(new contact("a","b",37));     contacts.add(new contact("a","c",34));     contacts.add(new contact("b","a",35));      collections.sort(contacts, (contact c1, contact c2) -> {         int firstnamecomparisonresult = c1.getfirstname().compareto(c2.getfirstname());         if (firstnamecomparisonresult != 0) {             return firstnamecomparisonresult;         } else {             return c1.getlastname().compareto(c2.getlastname());         }     });      system.out.println(contacts);  //[contact{firstname='a', lastname='b', age=37}, contact{firstname='a', lastname='c', age=34}, contact{firstname='b', lastname='a', age=35}]  }

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