折半查找，也称二分查找、二分搜索，是一种在有序数组中查找某一特定元素的搜索算法。

import java.util.Comparator;

/**
* 排序器接口(策略模式: 将算法封装到具有共同接口的独立的类中使得它们可以相互替换)
* @author骆昊
*
*/
public interface Sorter {

/**
* 排序
* @param list 待排序的数组
*/
public <T extends Comparable<T>> void sort(T[] list);

/**
* 排序
* @param list 待排序的数组
* @param comp 比较两个对象的比较器
*/
public <T> void sort(T[] list, Comparator<T> comp);
}

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import java.util.Comparator;

/**
* 冒泡排序
*
* @author骆昊
*
*/
public class BubbleSorter implements Sorter {

@Override
public <T extends Comparable<T>> void sort(T[] list) {
boolean swapped = true;
for (int i = 1, len = list.length; i < len && swapped; ++i) {
swapped = false;
for (int j = 0; j < len - i; ++j) {
if (list[j].compareTo(list[j + 1]) > 0) {
T temp = list[j];
list[j] = list[j + 1];
list[j + 1] = temp;
swapped = true;
}
}
}
}

@Override
public <T> void sort(T[] list, Comparator<T> comp) {
boolean swapped = true;
for (int i = 1, len = list.length; i < len && swapped; ++i) {
swapped = false;
for (int j = 0; j < len - i; ++j) {
if (comp.compare(list[j], list[j + 1]) > 0) {
T temp = list[j];
list[j] = list[j + 1];
list[j + 1] = temp;
swapped = true;
}
}
}
}
}

import java.util.Comparator;public
class MyUtil { public
static <T extends Comparable<T>> int
binarySearch(T[] x, T key) { return binarySearch(x,
0, x.length- 1, key); }
// 使用循环实现的二分查找 public
static <T> int
binarySearch(T[] x, T key, Comparator<T> comp) {
int low = 0; int high = x.length -
1; while (low <= high) {
int mid = (low + high) >>>
1; int cmp = comp.compare(x[mid], key);
if (cmp < 0) { low= mid +
1; } else if (cmp >
0) { high= mid - 1; }
else { return mid; } }
return -1; }
// 使用递归实现的二分查找 private
static<T extends Comparable<T>> int
binarySearch(T[] x, int low,
int high, T key) { if(low <= high) {
int mid = low + ((high -low) >> 1);
if(key.compareTo(x[mid])== 0) {
return mid; } else
if(key.compareTo(x[mid])< 0) {
return binarySearch(x,low, mid - 1, key); }
else { return binarySearch(x,mid +
1, high, key); } } return -1; }}