Java作為一種高級編程語言，其使用廣泛的算法和設計模式，可以大大提高編程效率和代碼質量。下面是Java中常見的算法和設計模式：

1. 排序算法：

public static void bubbleSort(int[] arr) {
int n = arr.length;
for (int i = 0; i< n - 1; i++) {
for (int j = 0; j< n - 1 - i; j++) {
if (arr[j] >arr[j + 1]) {
int temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
}
}
}

2. 查找算法：

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

3. 設計模式：

工廠模式：

public interface Product{
void show();
}
public class ConcreteProduct implements Product{
@Override
public void show() {
System.out.println("ConcreteProduct");
}
}
public interface Factory{
public Product create();
}
public class ConcreteFactory implements Factory{
@Override
public Product create() {
return new ConcreteProduct();
}
}

單例模式：

public class Singleton {
private static Singleton instance = null;
private Singleton() {}
public static Singleton getInstance() {
if (instance == null) {
synchronized (Singleton.class) {
if (instance == null) {
instance = new Singleton();
}
}
}
return instance;
}
}