1. Collections对整个序列的更改或排序操作
void reverse(List list) //List反转，返回更改后的List
void shuffle(List list) //进行随机混淆
void sort(List list) //按自然排序的升序排序
void sort(List list, Comparator c) //定制排序，由Comparator控制排序逻辑
void swap(List list, int i , int j) //交换两个索引位置的元素
void rotate(List list, int distance)//旋转。当distance为正数时，将list后distance个元素整体移到前面。当distance为负数时，将 list的前distance个元素整体移到后面。
示例代码：
public static void main(String[] args) {
ArrayList<Integer> arrayList = new ArrayList<Integer>();
arrayList.add(-1);
arrayList.add(3);
arrayList.add(3);
arrayList.add(-5);
arrayList.add(7);
System.out.println("原始数组:");
System.out.println(arrayList);
Collections.reverse(arrayList);
System.out.println("Collections.reverse(arrayList):");
System.out.println(arrayList);
Collections.rotate(arrayList, 4);
System.out.println("Collections.rotate(arrayList, 4):");
System.out.println(arrayList);
Collections.sort(arrayList);
System.out.println("Collections.sort(arrayList):");
System.out.println(arrayList);
Collections.shuffle(arrayList);
System.out.println("Collections.shuffle(arrayList):");
System.out.println(arrayList);
Collections.swap(arrayList, 1, 3);
System.out.println("Collections.swap(arrayList, 1, 3):");
System.out.println(arrayList);
// sort中重写compare方法，第一个参数减去第二个参数表示升序，第二个参数减去第一个参数表示降序
Collections.sort(arrayList, new Comparator<Integer>() {
@Override
public int compare(Integer integer, Integer t1) {
return t1 - integer;
}
});
System.out.println("定制排序后：");
System.out.println(arrayList);
}
2. Collections查找和基本替换操作（刷题常用）
int binarySearch(List list, Object key)//对List进行二分查找，返回索引，注意List必须是有序的
int max(Collection coll)//根据元素的自然顺序，返回最大的元素。 类比int min(Collection coll)
int max(Collection coll, Comparator c)//根据定制排序，返回最大元素，排序规则由Comparatator类控制。类比int min(Collection coll, Comparator c)
void fill(List list, Object obj)//用指定的元素代替指定list中的所有元素。
int frequency(Collection c, Object o)//统计元素出现次数
int indexOfSubList(List list, List target)//统计target在list中第一次出现的索引，找不到则返回-1，类比int lastIndexOfSubList(List source, list target).
boolean replaceAll(List list, Object oldVal, Object newVal) // 用新元素替换旧元素，全部替换
示例代码：
public static void main(String[] args) {
ArrayList<Integer> arrayList = new ArrayList<Integer>();
arrayList.add(-1);
arrayList.add(3);
arrayList.add(3);
arrayList.add(-5);
arrayList.add(7);
ArrayList<Integer> arrayList2 = new ArrayList<Integer>();
arrayList2.add(-3);
arrayList2.add(-3);
System.out.println("原始数组:");
System.out.println(arrayList);
System.out.println("Collections.max(arrayList):");
System.out.println(Collections.max(arrayList));
System.out.println("Collections.min(arrayList):");
System.out.println(Collections.min(arrayList, new Comparator<Integer>() {
@Override
public int compare(Integer integer, Integer t1) {
return integer - t1;
}
}));
System.out.println("Collections.replaceAll(arrayList, 3, -3):");
Collections.replaceAll(arrayList, 3, -3);
System.out.println(arrayList);
System.out.println("Collections.frequency(arrayList, -3):");
System.out.println(Collections.frequency(arrayList, -3));
System.out.println("Collections.indexOfSubList(arrayList, arrayList2):");
System.out.println(Collections.indexOfSubList(arrayList, arrayList2));
System.out.println("Collections.binarySearch(arrayList, -5):");
// 对List进行二分查找，返回索引，List必须是有序的
Collections.sort(arrayList);
System.out.println(Collections.binarySearch(arrayList, -5));
}
