参考大飞博客
http://brokendreams.iteye.com/blog/1913619

batchRemove方法

private boolean batchRemove(Collection c, boolean complement) {
final Object[] elementData = this.elementData;
int r = 0, w = 0;
boolean modified = false;
try {
for (; r < size; r++)
if (c.contains(elementData[r]) == complement)
elementData[w++] = elementData[r];
} finally {
// Preserve behavioral compatibility with AbstractCollection,
// even if c.contains() throws.
if (r != size) {
System.arraycopy(elementData, r,
elementData, w,
size - r);
w += size - r;
}
if (w != size) {
// clear to let GC do its work
for (int i = w; i < size; i++)
elementData[i] = null;
modCount += size - w;
size = w;
modified = true;
}
}
return modified;
}

这个方法是内部方法,就是批量删除.
加一些调试信息.

import java.util.*;
/**
* Hello world!
*/
public class App {
public static void main(String[] args) {
List l=new ArrayList();
l.add(3);
l.add(8);
batchRemove(l,true);
}
private static boolean batchRemove(Collection c, boolean complement) {
final Integer[] elementData = new Integer[]{1,2,3,4,5,6,7,8,9,10};
int size=elementData.length;
int r = 0, w = 0;
boolean modified = false;
try {
for (; r < size; r++) {
System.out.print("r:"+r+".."+"w:"+w+"..");
for (Integer i : elementData) {
System.out.print("," + i);
}
System.out.print("\n");
if (c.contains(elementData[r]) == complement) {
elementData[w++] = elementData[r];
}
}
} finally {
// Preserve behavioral compatibility with AbstractCollection,
// even if c.contains() throws.
if (r != size) {
System.arraycopy(elementData, r,
elementData, w,
size - r);
w += size - r;
}
if (w != size) {
// clear to let GC do its work
for (int i = w; i < size; i++)
elementData[i] = null;
size = w;
modified = true;
}
}
for(Integer i:elementData){
System.out.println("Data:"+i);
}
System.out.println("Size:"+size);
return modified;
}
}

r:0..w:0..,1,2,3,4,5,6,7,8,9,10
r:1..w:0..,1,2,3,4,5,6,7,8,9,10
r:2..w:0..,1,2,3,4,5,6,7,8,9,10
r:3..w:1..,3,2,3,4,5,6,7,8,9,10
r:4..w:1..,3,2,3,4,5,6,7,8,9,10
r:5..w:1..,3,2,3,4,5,6,7,8,9,10
r:6..w:1..,3,2,3,4,5,6,7,8,9,10
r:7..w:1..,3,2,3,4,5,6,7,8,9,10
r:8..w:2..,3,8,3,4,5,6,7,8,9,10
r:9..w:2..,3,8,3,4,5,6,7,8,9,10
Data:3
Data:8
Data:null
Data:null
Data:null
Data:null
Data:null
Data:null
Data:null
Data:null
Size:2

试试将complement改为false
batchRemove(l,false);
r:0..w:0..,1,2,3,4,5,6,7,8,9,10
r:1..w:1..,1,2,3,4,5,6,7,8,9,10
r:2..w:2..,1,2,3,4,5,6,7,8,9,10
r:3..w:2..,1,2,3,4,5,6,7,8,9,10
r:4..w:3..,1,2,4,4,5,6,7,8,9,10
r:5..w:4..,1,2,4,5,5,6,7,8,9,10
r:6..w:5..,1,2,4,5,6,6,7,8,9,10
r:7..w:6..,1,2,4,5,6,7,7,8,9,10
r:8..w:6..,1,2,4,5,6,7,7,8,9,10
r:9..w:7..,1,2,4,5,6,7,9,8,9,10
Data:1
Data:2
Data:4
Data:5
Data:6
Data:7
Data:9
Data:10
Data:null
Data:null
Size:8

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