47 * Serial warnings are suppressed throughout because all implementation
48 * classes use a serial proxy and thus have no need to declare serialVersionUID.
49 */
50 @SuppressWarnings("serial")
51 class ImmutableCollections {
52 /**
53 * A "salt" value used for randomizing iteration order. This is initialized once
54 * and stays constant for the lifetime of the JVM. It need not be truly random, but
55 * it needs to vary sufficiently from one run to the next so that iteration order
56 * will vary between JVM runs.
57 */
58 private static final long SALT32L;
59
60 /**
61 * For set and map iteration, we will iterate in "reverse" stochastically,
62 * decided at bootstrap time.
63 */
64 private static final boolean REVERSE;
65 static {
66 // to generate a reasonably random and well-mixed SALT, use an arbitrary
67 // value (a slice of pi), multiply with the System.nanoTime, then pick
68 // the mid 32-bits from the product. By picking a SALT value in the
69 // [0 ... 0xFFFF_FFFFL == 2^32-1] range, we ensure that for any positive
70 // int N, (SALT32L * N) >> 32 is a number in the [0 ... N-1] range. This
71 // property will be used to avoid more expensive modulo-based
72 // calculations.
73 long color = 0x243F_6A88_85A3_08D3L; // slice of pi
74 long seed = System.nanoTime();
75 SALT32L = (int)((color * seed) >> 16) & 0xFFFF_FFFFL;
76 // use the lowest bit to determine if we should reverse iteration
77 REVERSE = (SALT32L & 1) == 0;
78 }
79
80 /**
81 * Constants following this might be initialized from the CDS archive via
82 * this array.
83 */
84 private static Object[] archivedObjects;
85
86 private static final Object EMPTY;
87
88 static final ListN<?> EMPTY_LIST;
89
90 static final SetN<?> EMPTY_SET;
91
92 static final MapN<?,?> EMPTY_MAP;
93
94 static {
|
47 * Serial warnings are suppressed throughout because all implementation
48 * classes use a serial proxy and thus have no need to declare serialVersionUID.
49 */
50 @SuppressWarnings("serial")
51 class ImmutableCollections {
52 /**
53 * A "salt" value used for randomizing iteration order. This is initialized once
54 * and stays constant for the lifetime of the JVM. It need not be truly random, but
55 * it needs to vary sufficiently from one run to the next so that iteration order
56 * will vary between JVM runs.
57 */
58 private static final long SALT32L;
59
60 /**
61 * For set and map iteration, we will iterate in "reverse" stochastically,
62 * decided at bootstrap time.
63 */
64 private static final boolean REVERSE;
65 static {
66 // to generate a reasonably random and well-mixed SALT, use an arbitrary
67 // value (a slice of pi), multiply with a random seed, then pick
68 // the mid 32-bits from the product. By picking a SALT value in the
69 // [0 ... 0xFFFF_FFFFL == 2^32-1] range, we ensure that for any positive
70 // int N, (SALT32L * N) >> 32 is a number in the [0 ... N-1] range. This
71 // property will be used to avoid more expensive modulo-based
72 // calculations.
73 long color = 0x243F_6A88_85A3_08D3L; // slice of pi
74
75 // When running with -Xshare:dump, the VM will supply a "random" seed that's
76 // derived from the JVM build/version, so can we generate the exact same
77 // CDS archive for the same JDK build. This makes it possible to verify the
78 // consistency of the JDK build.
79 long seed = VM.getRandomSeedForCDSDump();
80 if (seed == 0) {
81 seed = System.nanoTime();
82 }
83 SALT32L = (int)((color * seed) >> 16) & 0xFFFF_FFFFL;
84 // use the lowest bit to determine if we should reverse iteration
85 REVERSE = (SALT32L & 1) == 0;
86 }
87
88 /**
89 * Constants following this might be initialized from the CDS archive via
90 * this array.
91 */
92 private static Object[] archivedObjects;
93
94 private static final Object EMPTY;
95
96 static final ListN<?> EMPTY_LIST;
97
98 static final SetN<?> EMPTY_SET;
99
100 static final MapN<?,?> EMPTY_MAP;
101
102 static {
|