rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicReferenceArray.java
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31 * Written by Doug Lea with assistance from members of JCP JSR-166
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36 package java.util.concurrent.atomic;
39 * An array of object references in which elements may be updated
40 * atomically. See the {@link java.util.concurrent.atomic} package
41 * specification for description of the properties of atomic
45 * @param <E> The base class of elements held in this array
47 public class AtomicReferenceArray<E> implements java.io.Serializable {
48 private static final long serialVersionUID = -6209656149925076980L;
50 private final Object[] array;
53 * Creates a new AtomicReferenceArray of the given length, with all
54 * elements initially null.
56 * @param length the length of the array
58 public AtomicReferenceArray(int length) {
59 array = new Object[length];
63 * Creates a new AtomicReferenceArray with the same length as, and
64 * all elements copied from, the given array.
66 * @param array the array to copy elements from
67 * @throws NullPointerException if array is null
69 public AtomicReferenceArray(E[] array) {
70 // Visibility guaranteed by final field guarantees
71 this.array = array.clone();
75 * Returns the length of the array.
77 * @return the length of the array
79 public final int length() {
84 * Gets the current value at position {@code i}.
87 * @return the current value
89 public final E get(int i) {
94 * Sets the element at position {@code i} to the given value.
97 * @param newValue the new value
99 public final void set(int i, E newValue) {
104 * Eventually sets the element at position {@code i} to the given value.
107 * @param newValue the new value
110 public final void lazySet(int i, E newValue) {
116 * Atomically sets the element at position {@code i} to the given
117 * value and returns the old value.
120 * @param newValue the new value
121 * @return the previous value
123 public final E getAndSet(int i, E newValue) {
130 * Atomically sets the element at position {@code i} to the given
131 * updated value if the current value {@code ==} the expected value.
134 * @param expect the expected value
135 * @param update the new value
136 * @return true if successful. False return indicates that
137 * the actual value was not equal to the expected value.
139 public final boolean compareAndSet(int i, E expect, E update) {
140 if (array[i] == expect) {
149 * Atomically sets the element at position {@code i} to the given
150 * updated value if the current value {@code ==} the expected value.
152 * <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
153 * and does not provide ordering guarantees, so is only rarely an
154 * appropriate alternative to {@code compareAndSet}.
157 * @param expect the expected value
158 * @param update the new value
159 * @return true if successful.
161 public final boolean weakCompareAndSet(int i, E expect, E update) {
162 return compareAndSet(i, expect, update);
166 * Returns the String representation of the current values of array.
167 * @return the String representation of the current values of array
169 public String toString() {
170 int iMax = array.length - 1;
174 StringBuilder b = new StringBuilder();
176 for (int i = 0; ; i++) {
179 return b.append(']').toString();
180 b.append(',').append(' ');