Attachment 198308 Details for Bug 317785 – General comparator test

General comparator test

TestComparator.java (text/x-java-source), 2.34 KB, created by Walter Laan

on 2011-06-21 03:42:23 EDT

(hide)

Description:

Filename:

MIME Type:

Creator: Walter Laan

Created: 2011-06-21 03:42:23 EDT

Size: 2.34 KB

patch

obsolete

>import java.util.Arrays;
>import java.util.Comparator;
>import java.util.List;
>
>public class TestComparator {
>    public static void main(String[] args) {
>        List<String> abc = Arrays.asList("a", "b", "c");
>        testComparator(String.CASE_INSENSITIVE_ORDER, abc, false);
>        testComparator(new Comparator<Object>() {
>            @Override
>            public int compare(Object o1, Object o2) {
>                return -1;
>            }
>        }, abc, false);
>    }
>
>    public static <T> void testComparator(Comparator<? super T> comparator,
>            List<T> sample, boolean consistentWithEquals) {
>
>        for(T x : sample) {
>            for(T y : sample) {
>                int xyResult = comparator.compare(x, y);
>                int yxResult = comparator.compare(y, x);
>                // sgn(compare(x, y)) == -sgn(compare(y, x)) for all x and y.
>                assert Math.signum(xyResult) == -Math.signum(yxResult) :
>                    String.format("sgn(compare(%1$s, %2$s)) != -sgn(compare(%2$s, %1$s))", x, y);
>
>                for(T z : sample) {
>                    int xzResult = comparator.compare(x, z);
>                    int yzResult = comparator.compare(y, z);
>                    // ((compare(x, y)>0) && (compare(y, z)>0)) implies compare(x, z)>0.
>                    if(xyResult > 0) {
>                        if(yzResult > 0) {
>                            assert xzResult > 0 : String.format(
>                                    "((compare(%1$s, %2$s)>0) && (compare(%2$s, %3$s)>0)) but not compare(%1$s, %3$s)>0", x, y, z);
>                        }
>                    }
>                    else if(xyResult == 0) {
>                        // compare(x, y)==0 implies that sgn(compare(x, z))==sgn(compare(y, z)) for all z.
>                        assert Math.signum(xzResult) == Math.signum(yzResult) : String.format(
>                                "compare(%1$s, %2$s)==0 but not that sgn(compare(%1$s, %3$s))==sgn(compare(%2$s, %3$s))", x, y, z);
>                    }
>                }
>
>                // Optionally (compare(x, y)==0) == (x.equals(y))
>                if(consistentWithEquals && xyResult == 0) {
>                    assert x.equals(y) : String.format(
>                            "compare(%1$s, %2$s)==0) == (%1$s.equals(%2$s)", x, y);
>                }
>            }
>        }
>    }
>}

Actions: View

Attachments on bug 317785: 172622 | 198111 | 198147 | 198271 | 198308