6891113: More methods for java.util.Objects: deepEquals, hash, toString with default
Reviewed-by: alanb, gafter
--- a/jdk/src/share/classes/java/util/Arrays.java Thu Oct 22 15:44:42 2009 +0100
+++ b/jdk/src/share/classes/java/util/Arrays.java Fri Oct 23 11:18:17 2009 -0700
@@ -3928,6 +3928,7 @@
* @param a2 the other array to be tested for equality
* @return <tt>true</tt> if the two arrays are equal
* @see #equals(Object[],Object[])
+ * @see Objects#deepEquals(Object, Object)
* @since 1.5
*/
public static boolean deepEquals(Object[] a1, Object[] a2) {
@@ -3949,27 +3950,7 @@
return false;
// Figure out whether the two elements are equal
- boolean eq;
- if (e1 instanceof Object[] && e2 instanceof Object[])
- eq = deepEquals ((Object[]) e1, (Object[]) e2);
- else if (e1 instanceof byte[] && e2 instanceof byte[])
- eq = equals((byte[]) e1, (byte[]) e2);
- else if (e1 instanceof short[] && e2 instanceof short[])
- eq = equals((short[]) e1, (short[]) e2);
- else if (e1 instanceof int[] && e2 instanceof int[])
- eq = equals((int[]) e1, (int[]) e2);
- else if (e1 instanceof long[] && e2 instanceof long[])
- eq = equals((long[]) e1, (long[]) e2);
- else if (e1 instanceof char[] && e2 instanceof char[])
- eq = equals((char[]) e1, (char[]) e2);
- else if (e1 instanceof float[] && e2 instanceof float[])
- eq = equals((float[]) e1, (float[]) e2);
- else if (e1 instanceof double[] && e2 instanceof double[])
- eq = equals((double[]) e1, (double[]) e2);
- else if (e1 instanceof boolean[] && e2 instanceof boolean[])
- eq = equals((boolean[]) e1, (boolean[]) e2);
- else
- eq = e1.equals(e2);
+ boolean eq = deepEquals0(e1, e2);
if (!eq)
return false;
@@ -3977,6 +3958,32 @@
return true;
}
+ static boolean deepEquals0(Object e1, Object e2) {
+ assert e1 != null;
+ boolean eq;
+ if (e1 instanceof Object[] && e2 instanceof Object[])
+ eq = deepEquals ((Object[]) e1, (Object[]) e2);
+ else if (e1 instanceof byte[] && e2 instanceof byte[])
+ eq = equals((byte[]) e1, (byte[]) e2);
+ else if (e1 instanceof short[] && e2 instanceof short[])
+ eq = equals((short[]) e1, (short[]) e2);
+ else if (e1 instanceof int[] && e2 instanceof int[])
+ eq = equals((int[]) e1, (int[]) e2);
+ else if (e1 instanceof long[] && e2 instanceof long[])
+ eq = equals((long[]) e1, (long[]) e2);
+ else if (e1 instanceof char[] && e2 instanceof char[])
+ eq = equals((char[]) e1, (char[]) e2);
+ else if (e1 instanceof float[] && e2 instanceof float[])
+ eq = equals((float[]) e1, (float[]) e2);
+ else if (e1 instanceof double[] && e2 instanceof double[])
+ eq = equals((double[]) e1, (double[]) e2);
+ else if (e1 instanceof boolean[] && e2 instanceof boolean[])
+ eq = equals((boolean[]) e1, (boolean[]) e2);
+ else
+ eq = e1.equals(e2);
+ return eq;
+ }
+
/**
* Returns a string representation of the contents of the specified array.
* The string representation consists of a list of the array's elements,
--- a/jdk/src/share/classes/java/util/Objects.java Thu Oct 22 15:44:42 2009 +0100
+++ b/jdk/src/share/classes/java/util/Objects.java Fri Oct 23 11:18:17 2009 -0700
@@ -33,7 +33,7 @@
*
* @since 1.7
*/
-public class Objects {
+public final class Objects {
private Objects() {
throw new AssertionError("No java.util.Objects instances for you!");
}
@@ -57,6 +57,32 @@
return (a == b) || (a != null && a.equals(b));
}
+ /**
+ * Returns {@code true} if the arguments are deeply equal to each other
+ * and {@code false} otherwise.
+ *
+ * Two {@code null} values are deeply equal. If both arguments are
+ * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
+ * Object[]) Arrays.deepEquals} is used to determine equality.
+ * Otherwise, equality is determined by using the {@link
+ * Object#equals equals} method of the first argument.
+ *
+ * @param a an object
+ * @param b an object to be compared with {@code a} for deep equality
+ * @return {@code true} if the arguments are deeply equal to each other
+ * and {@code false} otherwise
+ * @see Arrays#deepEquals(Object[], Object[])
+ * @see Objects#equals(Object, Object)
+ */
+ public static boolean deepEquals(Object a, Object b) {
+ if (a == b)
+ return true;
+ else if (a == null || b == null)
+ return false;
+ else
+ return Arrays.deepEquals0(a, b);
+ }
+
/**
* Returns the hash code of a non-{@code null} argument and 0 for
* a {@code null} argument.
@@ -70,6 +96,36 @@
return o != null ? o.hashCode() : 0;
}
+ /**
+ * Generates a hash code for a sequence of input values. The hash
+ * code is generated as if all the input values were placed into an
+ * array, and that array were hashed by calling {@link
+ * Arrays#hashCode(Object[])}.
+ *
+ * <p>This method is useful for implementing {@link
+ * Object#hashCode()} on objects containing multiple fields. For
+ * example, if an object that has three fields, {@code x}, {@code
+ * y}, and {@code z}, one could write:
+ *
+ * <blockquote><pre>
+ * @Override public int hashCode() {
+ * return Objects.hash(x, y, z);
+ * }
+ * </pre></blockquote>
+ *
+ * <b>Warning: When a single object reference is supplied, the returned
+ * value does not equal the hash code of that object reference.</b> This
+ * value can be computed by calling {@link #hashCode(Object)}.
+ *
+ * @param values the values to be hashed
+ * @return a hash value of the sequence of input values
+ * @see Arrays#hashCode
+ * @see List#hashCode
+ */
+ public static int hash(Object... values) {
+ return Arrays.hashCode(values);
+ }
+
/**
* Returns the result of calling {@code toString} for a non-{@code
* null} argument and {@code "null"} for a {@code null} argument.
@@ -85,6 +141,23 @@
}
/**
+ * Returns the result of calling {@code toString} on the first
+ * argument if the first argument is not {@code null} and returns
+ * the second argument otherwise.
+ *
+ * @param o an object
+ * @param nullDefault string to return if the first argument is
+ * {@code null}
+ * @return the result of calling {@code toString} on the first
+ * argument if it is not {@code null} and the second argument
+ * otherwise.
+ * @see Objects#toString(Object)
+ */
+ public static String toString(Object o, String nullDefault) {
+ return (o != null) ? o.toString() : nullDefault;
+ }
+
+ /**
* Returns 0 if the arguments are identical and {@code
* c.compare(a, b)} otherwise.
* Consequently, if both arguments are {@code null} 0
--- a/jdk/test/java/util/Objects/BasicObjectsTest.java Thu Oct 22 15:44:42 2009 +0100
+++ b/jdk/test/java/util/Objects/BasicObjectsTest.java Fri Oct 23 11:18:17 2009 -0700
@@ -23,7 +23,7 @@
/*
* @test
- * @bug 6797535
+ * @bug 6797535 6889858 6891113
* @summary Basic tests for methods in java.util.Objects
* @author Joseph D. Darcy
*/
@@ -34,8 +34,11 @@
public static void main(String... args) {
int errors = 0;
errors += testEquals();
+ errors += testDeepEquals();
errors += testHashCode();
+ errors += testHash();
errors += testToString();
+ errors += testToString2();
errors += testCompare();
errors += testNonNull();
if (errors > 0 )
@@ -60,6 +63,36 @@
return errors;
}
+ private static int testDeepEquals() {
+ int errors = 0;
+ Object[] values = {null,
+ null, // Change to values later
+ new byte[] {(byte)1},
+ new short[] {(short)1},
+ new int[] {1},
+ new long[] {1L},
+ new char[] {(char)1},
+ new float[] {1.0f},
+ new double[]{1.0d},
+ new String[]{"one"}};
+ values[1] = values;
+
+ for(int i = 0; i < values.length; i++)
+ for(int j = 0; j < values.length; j++) {
+ boolean expected = (i == j);
+ Object a = values[i];
+ Object b = values[j];
+ boolean result = Objects.deepEquals(a, b);
+ if (result != expected) {
+ errors++;
+ System.err.printf("When equating %s to %s, got %b instead of %b%n.",
+ a, b, result, expected);
+ }
+ }
+
+ return errors;
+ }
+
private static int testHashCode() {
int errors = 0;
errors += (Objects.hashCode(null) == 0 ) ? 0 : 1;
@@ -68,6 +101,19 @@
return errors;
}
+ private static int testHash() {
+ int errors = 0;
+
+ Object[] data = new String[]{"perfect", "ham", "THC"};
+
+ errors += ((Objects.hash((Object[])null) == 0) ? 0 : 1);
+
+ errors += (Objects.hash("perfect", "ham", "THC") ==
+ Arrays.hashCode(data)) ? 0 : 1;
+
+ return errors;
+ }
+
private static int testToString() {
int errors = 0;
errors += ("null".equals(Objects.toString(null)) ) ? 0 : 1;
@@ -76,6 +122,14 @@
return errors;
}
+ private static int testToString2() {
+ int errors = 0;
+ String s = "not the default";
+ errors += (s.equals(Objects.toString(null, s)) ) ? 0 : 1;
+ errors += (s.equals(Objects.toString(s, "another string")) ) ? 0 : 1;
+ return errors;
+ }
+
private static int testCompare() {
int errors = 0;
String[] values = {"e. e. cummings", "zzz"};