OnJava8-Examples/arrays/ComparatorTest.java

// arrays/ComparatorTest.java
// (c)2016 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
// Implementing a Comparator for a class
import java.util.*;
import onjava.*;
import static onjava.ArrayShow.*;

class CompTypeComparator implements Comparator<CompType> {
  public int compare(CompType o1, CompType o2) {
    return (o1.j < o2.j ? -1 : (o1.j == o2.j ? 0 : 1));
  }
}

public class ComparatorTest {
  public static void main(String[] args) {
    CompType[] a = new CompType[12];
    Arrays.setAll(a, n -> CompType.get());
    show("Before sorting", a);
    Arrays.sort(a, new CompTypeComparator());
    show("After sorting", a);
  }
}
/* Output:
before sorting:
[[i = 58, j = 55], [i = 93, j = 61], [i = 61, j = 29]
, [i = 68, j = 0], [i = 22, j = 7], [i = 88, j = 28]
, [i = 51, j = 89], [i = 9, j = 78], [i = 98, j = 61]
, [i = 20, j = 58], [i = 16, j = 40], [i = 11, j = 22]
]
after sorting:
[[i = 68, j = 0], [i = 22, j = 7], [i = 11, j = 22]
, [i = 88, j = 28], [i = 61, j = 29], [i = 16, j = 40]
, [i = 58, j = 55], [i = 20, j = 58], [i = 93, j = 61]
, [i = 98, j = 61], [i = 9, j = 78], [i = 51, j = 89]
]
*/