binarySearch原理：
public static index halfSearch(List<String> list, String key)
{
int max,min,mid;
max = list.size()-1;
min = 0;
while(min<=max)
{
mid = (max+min) >>1;
String str = list.get(mid);
int num = str.compareTo(key);
if(num > 0)
max = mid – 1;
else if(num < 0)
min = min + 1;
return min;//如果是Collections.binarySearch()，它是在min后面的位置-(接入点) - 1
}
}
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Collections.fill(list, “pp”);
将集合中的元素全部替换成为pp
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Collections.replaceAll(list, “oldValue”, “newValue”);
相同于：
list.set(index, “newValue”);
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Collections.reverse(list);
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Collections.swap(list, 1, 2);//角标1、角标2对换
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Collections.shuffle(list);//随机排列list
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