edu.emory.mathcs.backport.java.util.concurrent.atomic.AtomicReferenceArray Maven / Gradle / Ivy
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/*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/licenses/publicdomain
*/
package edu.emory.mathcs.backport.java.util.concurrent.atomic;
/**
* An array of object references in which elements may be updated
* atomically. See the {@link edu.emory.mathcs.backport.java.util.concurrent.atomic} package
* specification for description of the properties of atomic
* variables.
* @since 1.5
* @author Doug Lea
*/
public class AtomicReferenceArray implements java.io.Serializable {
private static final long serialVersionUID = -6209656149925076980L;
private final Object[] array;
/**
* Creates a new AtomicReferenceArray of given length.
* @param length the length of the array
*/
public AtomicReferenceArray(int length) {
array = new Object[length];
}
/**
* Creates a new AtomicReferenceArray with the same length as, and
* all elements copied from, the given array.
*
* @param array the array to copy elements from
* @throws NullPointerException if array is null
*/
public AtomicReferenceArray(Object[] array) {
if (array == null)
throw new NullPointerException();
int length = array.length;
this.array = new Object[length];
System.arraycopy(array, 0, this.array, 0, array.length);
}
/**
* Returns the length of the array.
*
* @return the length of the array
*/
public final int length() {
return array.length;
}
/**
* Gets the current value at position {@code i}.
*
* @param i the index
* @return the current value
*/
public final synchronized Object get(int i) {
return array[i];
}
/**
* Sets the element at position {@code i} to the given value.
*
* @param i the index
* @param newValue the new value
*/
public final synchronized void set(int i, Object newValue) {
array[i] = newValue;
}
/**
* Eventually sets the element at position {@code i} to the given value.
*
* @param i the index
* @param newValue the new value
* @since 1.6
*/
public final synchronized void lazySet(int i, Object newValue) {
array[i] = newValue;
}
/**
* Atomically sets the element at position {@code i} to the given
* value and returns the old value.
*
* @param i the index
* @param newValue the new value
* @return the previous value
*/
public final synchronized Object getAndSet(int i, Object newValue) {
Object old = array[i];
array[i] = newValue;
return old;
}
/**
* Atomically sets the element at position {@code i} to the given
* updated value if the current value {@code ==} the expected value.
* @param i the index
* @param expect the expected value
* @param update the new value
* @return true if successful. False return indicates that
* the actual value was not equal to the expected value.
*/
public final synchronized boolean compareAndSet(int i, Object expect, Object update) {
if (array[i] == expect) {
array[i] = update;
return true;
}
else {
return false;
}
}
/**
* Atomically sets the element at position {@code i} to the given
* updated value if the current value {@code ==} the expected value.
*
* May fail spuriously
* and does not provide ordering guarantees, so is only rarely an
* appropriate alternative to {@code compareAndSet}.
*
* @param i the index
* @param expect the expected value
* @param update the new value
* @return true if successful.
*/
public final synchronized boolean weakCompareAndSet(int i, Object expect, Object update) {
if (array[i] == expect) {
array[i] = update;
return true;
}
else {
return false;
}
}
/**
* Returns the String representation of the current values of array.
* @return the String representation of the current values of array.
*/
public synchronized String toString() {
if (array.length == 0)
return "[]";
StringBuffer buf = new StringBuffer();
for (int i = 0; i < array.length; i++) {
if (i == 0)
buf.append('[');
else
buf.append(", ");
buf.append(String.valueOf(array[i]));
}
buf.append("]");
return buf.toString();
}
}