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修改CopyOnWrite部分的表述

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This commit is contained in:
xiangflight 2018-07-12 15:15:06 +08:00
parent 08457794f7
commit e7d694d841
1 changed files with 10 additions and 5 deletions
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9
notes/Java 容器.md
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@ -255,7 +255,8 @@ List<String> synList = Collections.synchronizedList(list);
List<String> list = new CopyOnWriteArrayList<>(); List<String> list = new CopyOnWriteArrayList<>();
``` ```
扩展：CopyOnWriteArrayList是一种CopyOnWrite容器，即写时复制的容器。从以下源码中看出：当向容器中添加元素时，不是直接往当前容器添加，而是Copy当前容器，在新容器中添加，添加完后，将原容器的引用指向新容器。这样做可以对CopyOnWrite容器进行并发的读，不需要加锁，极大地提高了读性能，因此适用于读多写少的场景。 扩展
CopyOnWriteArrayList是一种CopyOnWrite容器，从以下源码看出：添加元素是在复制的新数组上进行的，然后将原数组的引用指向新数组；读取元素是从原数组读取。这样可以进行并发的且不需加锁的读取，读取效率高，适用于读操作远大于写操作的场景中。
```java ```java
public boolean add(E e) { public boolean add(E e) {
@ -264,7 +265,7 @@ public boolean add(E e) {
try { try {
Object[] elements = getArray(); Object[] elements = getArray();
int len = elements.length; int len = elements.length;
Object[] newElements = Arrays.copyOf(elements, len + 1); // 复制到新容器 Object[] newElements = Arrays.copyOf(elements, len + 1);
newElements[len] = e; newElements[len] = e;
setArray(newElements); setArray(newElements);
return true; return true;
@ -273,6 +274,10 @@ public boolean add(E e) {
} }
} }
final void setArray(Object[] a) {
array = a;
}
@SuppressWarnings("unchecked") @SuppressWarnings("unchecked")
private E get(Object[] a, int index) { private E get(Object[] a, int index) {
return (E) a[index]; return (E) a[index];