Java作為一門強大的編程語言，在常用算法分析與實現方面也有非常豐富的資源。以下是幾種常用的算法及其Java實現。

1. 快速排序

public static void quickSort(int[] arr, int left, int right) {
if (left >= right) {
return;
}
int pivot = arr[(left + right) / 2];
int index = partition(arr, left, right, pivot);
quickSort(arr, left, index - 1);
quickSort(arr, index, right);
}
private static int partition(int[] arr, int left, int right, int pivot) {
while (left<= right) {
while (arr[left]< pivot) {
left++;
}
while (arr[right] >pivot) {
right--;
}
if (left<= right) {
swap(arr, left, right);
left++;
right--;
}
}
return left;
}
private static void swap(int[] arr, int i, int j) {
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}

2. 歸并排序

public static void mergeSort(int[] arr, int left, int right) {
if (left == right) {
return;
}
int mid = (left + right) / 2;
mergeSort(arr, left, mid);
mergeSort(arr, mid + 1, right);
merge(arr, left, mid, right);
}
private static void merge(int[] arr, int left, int mid, int right) {
int[] temp = new int[arr.length];
int i = left;
int j = mid + 1;
int k = left;
while (i<= mid && j<= right) {
if (arr[i]< arr[j]) {
temp[k++] = arr[i++];
} else {
temp[k++] = arr[j++];
}
}
while (i<= mid) {
temp[k++] = arr[i++];
}
while (j<= right) {
temp[k++] = arr[j++];
}
for (int l = left; l<= right; l++) {
arr[l] = temp[l];
}
}

3. 二分查找

public static int binarySearch(int[] arr, int key) {
int start = 0;
int end = arr.length - 1;
while (start<= end) {
int mid = (start + end) / 2;
if (key == arr[mid]) {
return mid;
} else if (key< arr[mid]) {
end = mid - 1;
} else {
start = mid + 1;
}
}
return -1;
}

4. 斐波那契數列

public static int fibonacci(int n) {
if (n<= 1) {
return n;
}
int fib = 1;
int prevFib = 1;
for (int i = 2; i< n; i++) {
int temp = fib;
fib += prevFib;
prevFib = temp;
}
return fib;
}

總結

以上是幾種常用的算法及其Java實現，它們在不同的場景中發揮著重要的作用。在編寫算法時，我們需要結合具體的應用場景，選擇合適的算法，并通過不斷優化和改進提高算法的效率。