java - Abstract Data Types, sorting objects by specific variable in a list -

alright here go.

i made adt in form of sortedarraylist, has add method looking this:

public boolean addtoarray(t i)     {               int insertplace = 0;                  for(int j=0;j<size;j++)                 {                       if(i.compareto(sortedarray[j])<0)                     {                         insertplace =j;                         j = size;                     }                 }                 if(size>0)                 {                           for(int w=size-1; w>=insertplace;w--)                         {                                 sortedarray[size]=sortedarray[w];                         }                         sortedarray[insertplace]=i;                 }                 else                 {                     sortedarray[0]=i;                 }                 size++;            return true;       } 

now, works wonders sorted adt when input strings. however, instead of strings, want add objects list in shape of persons, object containing 4 variables(string country, string name, int age, int cpr). want person objects sorted in list age.

here person class compareto method sorting.

public class person implements comparable<person> {     int cpr=200193;     int age=21;     string name="john doe";     string country="uzbekistan";       public person() {         this.cpr=cpr;         this.age=age;     }     public person(string name, string country,int cpr,int age)      {         this.cpr=cpr;         this.age=age;         this.name=name;         this.country=country;     }       @override     public string tostring()     {         return "person [country= " + country + ", name:" + name + ", cpr: "+cpr+ ", age: "+age+"]";     }      public int compareto(person p)     {         int before=-1;         int after=1;         int middle=0;           if(this.age!=p.age)         {             if(this.age>p.age)              {                 return before;             }               if(this.age<p.age)             {                 return after;             }         }         return middle;     } 

now, problem objects sorted, since not appear in same order call them list. can't figure out how sorted , how make objects sorted age in list.

edit

p1.addtoarray(new person()); p1.addtoarray(new person("pete","germany",111111,86)); p1.addtoarray(new person("john","denmark",123456,75)); p1.addtoarray(new person("michael jackson", "america",112345,49)); 

output:

item: person [country= america, name:michael jackson, cpr: 112345, age: 49] item: person [country= uzbekistan, name:john doe, cpr: 200193, age: 21] item: person [country= germany, name:pete, cpr: 111111, age: 86] item: person [country= denmark, name:john, cpr: 123456, age: 75] 

i don't think sorting function works:

my test:

static void test() {     addtoarray("zello");     addtoarray("boby");     addtoarray("amy");     addtoarray("coco");     addtoarray("boris");     for(int = 0; < size; i++) {         system.out.println(sortedarray[i]);     } } 

output:

amy boris boby zello coco 

here different , more efficient way it.

use arrays.binarysearch() find proper insertion position. mind you, function returns:

• the index of value if exists.
• the -(insertposition - 1) if value doesn't exist.

i assume based on code size variable represents index of last element in array. means initialize -1 when array empty.

furthermore, think don't allow duplicates , each person unique solution returns false when try insert duplicate.

of course, make sure resize array after criterium matched (usually when array half full).

public boolean addtoarray(t item) {      if (item == null) {         return false;     } else if (size == -1) {         size++;         sortedarray[size] = item;         return true;     } else {          // find correct insertion point using binary search         int insertionpoint = arrays                 .binarysearch(sortedarray, 0, size+1, item);          if (insertionpoint >= 0) {             // duplicate value             return false;         }          // set insertionpoint proper value         insertionpoint = (-(insertionpoint) - 1);          // shift elements right of insertionpoint         (int = size + 1; > insertionpoint; i--) {             sortedarray[i] = sortedarray[i - 1];         }          // insert @ insertionpoint         sortedarray[insertionpoint] = item;          // update size         size++;          return true; //success     } } 

also, can further simplify compareto() method in person object.

public int compareto(person p) {     if(p != null) {             return p.age - this.age;     } else throw new nullpointerexception(); } 

right now, sorting descending. if want make ascending, change:

return p.age - this.age; 

to:

return this.age - p.age; 

here full running example

example output (with ascending sort):

person [country= uzbekistan, name:john doe, cpr: 200193, age: 21] person [country= america, name:michael jackson, cpr: 112345, age: 49] person [country= denmark, name:john, cpr: 123456, age: 75] person [country= germany, name:pete, cpr: 111111, age: 86]