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自己做网站要学什么软件下载,wordpress 订餐模板,wordpress读取菜单,室内装修设计图效果图目录 一、Java算法生态#xff1a;集合框架与流式编程 1.1 Java算法的演进历程 1.2 集合框架中的算法 二、Stream API#xff1a;声明式算法编程 2.1 Stream操作的三阶段 2.2 高级Stream操作 三、排序与搜索算法 3.1 对象排序的多种方式 3.2 搜索算法实现 四、数值…目录一、Java算法生态集合框架与流式编程1.1 Java算法的演进历程1.2 集合框架中的算法二、Stream API声明式算法编程2.1 Stream操作的三阶段2.2 高级Stream操作三、排序与搜索算法3.1 对象排序的多种方式3.2 搜索算法实现四、数值计算与统计4.1 基本数值算法4.2 统计与聚合算法五、字符串处理算法5.1 字符串匹配与操作六、并发与并行算法6.1 并行流与Fork/Join框架6.2 并发集合算法七、图算法实现7.1 图的表示与遍历八、设计模式在算法中的应用8.1 策略模式实现排序算法如果您喜欢此文章请收藏、点赞、评论谢谢祝您快乐每一天。一、Java算法生态集合框架与流式编程1.1 Java算法的演进历程Java算法设计经历了三个重要阶段JDK 1.2Collections Framework引入奠定算法基础JDK 5泛型、并发集合、增强for循环JDK 8Stream API、Lambda表达式、函数式编程革命1.2 集合框架中的算法// Collections工具类中的静态算法方法ListInteger numbers Arrays.asList(3, 1, 4, 1, 5, 9, 2, 6);// 1. 排序算法Collections.sort(numbers); // 升序排序Collections.sort(numbers, Collections.reverseOrder()); // 降序排序Collections.shuffle(numbers); // 随机打乱// 2. 查找算法int index Collections.binarySearch(numbers, 5); // 二分查找int freq Collections.frequency(numbers, 1); // 出现频率// 3. 极值算法Integer max Collections.max(numbers);Integer min Collections.min(numbers);// 4. 不可变集合ListInteger unmodifiable Collections.unmodifiableList(numbers);SetInteger singleton Collections.singleton(42);ListInteger nCopies Collections.nCopies(5, 0); // [0, 0, 0, 0, 0]二、Stream API声明式算法编程2.1 Stream操作的三阶段// 创建 → 中间操作 → 终止操作ListInteger result numbers.stream() // 创建流.filter(n - n % 2 0) // 中间操作过滤.map(n - n * n) // 中间操作映射.sorted((a, b) - b - a) // 中间操作排序.distinct() // 中间操作去重.limit(3) // 中间操作限制.collect(Collectors.toList()); // 终止操作收集// 并行流加速处理long count numbers.parallelStream().filter(n - isPrime(n)).count();2.2 高级Stream操作// 1. 分组与分区MapString, ListEmployee byDept employees.stream().collect(Collectors.groupingBy(Employee::getDepartment));MapBoolean, ListEmployee partitioned employees.stream().collect(Collectors.partitioningBy(e - e.getSalary() 50000));// 2. 统计汇总IntSummaryStatistics stats employees.stream().mapToInt(Employee::getSalary).summaryStatistics();// 包含count, sum, min, max, average// 3. 连接字符串String names employees.stream().map(Employee::getName).collect(Collectors.joining(, , [, ]));// 4. 归约操作OptionalInteger total numbers.stream().reduce((a, b) - a b); // 求和Integer sum numbers.stream().reduce(0, Integer::sum); // 带初始值的求和// 5. 自定义收集器CollectorEmployee, ?, MapString, Double avgSalaryByDept Collectors.groupingBy(Employee::getDepartment,Collectors.averagingDouble(Employee::getSalary));三、排序与搜索算法3.1 对象排序的多种方式// 1. 实现Comparable接口class Person implements ComparablePerson {private String name;private int age;Overridepublic int compareTo(Person other) {return Integer.compare(this.age, other.age);}}// 2. 使用Comparator更灵活ComparatorPerson byName Comparator.comparing(Person::getName);ComparatorPerson byAge Comparator.comparingInt(Person::getAge);ComparatorPerson byNameThenAge Comparator.comparing(Person::getName).thenComparingInt(Person::getAge);// 3. 复杂排序ListPerson sorted people.stream().sorted(Comparator.comparing(Person::getLastName).thenComparing(Person::getFirstName).reversed()).collect(Collectors.toList());// 4. 处理null值ComparatorPerson nullsFirst Comparator.nullsFirst(Comparator.naturalOrder());3.2 搜索算法实现// 1. 二分查找数组必须有序int[] sortedArray {1, 3, 5, 7, 9, 11, 13};int index Arrays.binarySearch(sortedArray, 7); // 返回3// 2. 自定义二分查找public static T int binarySearch(List? extends T list, T key,Comparator? super T c) {int low 0;int high list.size() - 1;while (low high) {int mid (low high) 1; // 无符号右移防止溢出T midVal list.get(mid);int cmp c.compare(midVal, key);if (cmp 0) {low mid 1;} else if (cmp 0) {high mid - 1;} else {return mid; // 找到}}return -(low 1); // 未找到返回插入点}// 3. 使用Collections.binarySearchListString words Arrays.asList(apple, banana, cherry, date);int pos Collections.binarySearch(words, cherry);四、数值计算与统计4.1 基本数值算法// 1. 使用Math类double sqrt Math.sqrt(16.0); // 4.0double pow Math.pow(2, 10); // 1024.0double sin Math.sin(Math.PI / 2); // 1.0long round Math.round(3.14159); // 3// 2. 随机数生成Random random new Random();int randomInt random.nextInt(100); // 0-99double randomDouble random.nextDouble(); // 0.0-1.0// 3. 安全的随机数密码学安全SecureRandom secureRandom new SecureRandom();byte[] randomBytes new byte[16];secureRandom.nextBytes(randomBytes);// 4. 大数计算BigInteger bigInt new BigInteger(12345678901234567890);BigInteger result bigInt.multiply(new BigInteger(2));BigDecimal decimal1 new BigDecimal(10.50);BigDecimal decimal2 new BigDecimal(3.75);BigDecimal division decimal1.divide(decimal2, 4, RoundingMode.HALF_UP);4.2 统计与聚合算法// 1. 基本统计public class Statistics {public static double mean(double[] values) {return Arrays.stream(values).average().orElse(0.0);}public static double median(double[] values) {double[] sorted values.clone();Arrays.sort(sorted);int n sorted.length;if (n % 2 0) {return (sorted[n/2 - 1] sorted[n/2]) / 2.0;} else {return sorted[n/2];}}public static double standardDeviation(double[] values) {double mean mean(values);double variance Arrays.stream(values).map(x - Math.pow(x - mean, 2)).average().orElse(0.0);return Math.sqrt(variance);}}// 2. 使用DoubleSummaryStatisticsDoubleSummaryStatistics stats Arrays.stream(new double[]{1.0, 2.0, 3.0, 4.0}).summaryStatistics();// 3. 移动平均public static double[] movingAverage(double[] data, int window) {double[] result new double[data.length - window 1];double sum 0;for (int i 0; i window; i) {sum data[i];}result[0] sum / window;for (int i window; i data.length; i) {sum sum - data[i - window] data[i];result[i - window 1] sum / window;}return result;}五、字符串处理算法5.1 字符串匹配与操作// 1. KMP字符串匹配算法public class KMP {public static int search(String text, String pattern) {int[] lps computeLPS(pattern);int i 0, j 0;while (i text.length()) {if (text.charAt(i) pattern.charAt(j)) {i;j;if (j pattern.length()) {return i - j;}} else {if (j ! 0) {j lps[j - 1];} else {i;}}}return -1;}private static int[] computeLPS(String pattern) {int[] lps new int[pattern.length()];int len 0, i 1;while (i pattern.length()) {if (pattern.charAt(i) pattern.charAt(len)) {len;lps[i] len;i;} else {if (len ! 0) {len lps[len - 1];} else {lps[i] 0;i;}}}return lps;}}// 2. 字符串编辑距离动态规划public static int editDistance(String word1, String word2) {int m word1.length();int n word2.length();int[][] dp new int[m 1][n 1];for (int i 0; i m; i) dp[i][0] i;for (int j 0; j n; j) dp[0][j] j;for (int i 1; i m; i) {for (int j 1; j n; j) {if (word1.charAt(i - 1) word2.charAt(j - 1)) {dp[i][j] dp[i - 1][j - 1];} else {dp[i][j] 1 Math.min(dp[i - 1][j - 1], // 替换Math.min(dp[i - 1][j], // 删除dp[i][j - 1] // 插入));}}}return dp[m][n];}// 3. 使用StringBuilder优化字符串操作public static String reverseString(String s) {return new StringBuilder(s).reverse().toString();}public static boolean isPalindrome(String s) {String cleaned s.replaceAll([^a-zA-Z0-9], ).toLowerCase();return cleaned.equals(new StringBuilder(cleaned).reverse().toString());}六、并发与并行算法6.1 并行流与Fork/Join框架// 1. 并行流计算long sum LongStream.rangeClosed(1, 10_000_000).parallel().sum();// 2. 自定义Fork/Join任务class SumTask extends RecursiveTaskLong {private static final int THRESHOLD 10_000;private final long[] array;private final int start, end;SumTask(long[] array, int start, int end) {this.array array;this.start start;this.end end;}Overrideprotected Long compute() {if (end - start THRESHOLD) {long sum 0;for (int i start; i end; i) {sum array[i];}return sum;} else {int mid (start end) / 2;SumTask left new SumTask(array, start, mid);SumTask right new SumTask(array, mid, end);left.fork();long rightResult right.compute();long leftResult left.join();return leftResult rightResult;}}}// 使用Fork/Join池ForkJoinPool pool new ForkJoinPool();long[] numbers new long[100_000];// 填充数组...SumTask task new SumTask(numbers, 0, numbers.length);long result pool.invoke(task);6.2 并发集合算法// 1. ConcurrentHashMap的原子操作ConcurrentHashMapString, Integer map new ConcurrentHashMap();// 线程安全的更新map.compute(key, (k, v) - v null ? 1 : v 1);// 原子操作map.merge(key, 1, Integer::sum);// 2. CopyOnWriteArrayList读多写少场景CopyOnWriteArrayListString list new CopyOnWriteArrayList();list.add(item1);list.addIfAbsent(item1); // 不会重复添加// 3. 阻塞队列算法BlockingQueueInteger queue new LinkedBlockingQueue(10);// 生产者new Thread(() - {try {for (int i 0; i 100; i) {queue.put(i); // 阻塞直到有空间Thread.sleep(100);}} catch (InterruptedException e) {Thread.currentThread().interrupt();}}).start();// 消费者new Thread(() - {try {while (true) {Integer item queue.take(); // 阻塞直到有元素System.out.println(Consumed: item);}} catch (InterruptedException e) {Thread.currentThread().interrupt();}}).start();七、图算法实现7.1 图的表示与遍历// 1. 邻接表表示class Graph {private final int V;private final ListListInteger adj;public Graph(int V) {this.V V;adj new ArrayList(V);for (int i 0; i V; i) {adj.add(new ArrayList());}}public void addEdge(int v, int w) {adj.get(v).add(w);}// 深度优先搜索public void dfs(int start) {boolean[] visited new boolean[V];StackInteger stack new Stack();stack.push(start);while (!stack.isEmpty()) {int v stack.pop();if (!visited[v]) {visited[v] true;System.out.print(v );for (int neighbor : adj.get(v)) {if (!visited[neighbor]) {stack.push(neighbor);}}}}}// 广度优先搜索public void bfs(int start) {boolean[] visited new boolean[V];QueueInteger queue new LinkedList();visited[start] true;queue.offer(start);while (!queue.isEmpty()) {int v queue.poll();System.out.print(v );for (int neighbor : adj.get(v)) {if (!visited[neighbor]) {visited[neighbor] true;queue.offer(neighbor);}}}}}// 2. Dijkstra最短路径算法public class Dijkstra {public static int[] dijkstra(int[][] graph, int src) {int V graph.length;int[] dist new int[V];boolean[] sptSet new boolean[V];Arrays.fill(dist, Integer.MAX_VALUE);dist[src] 0;for (int count 0; count V - 1; count) {int u minDistance(dist, sptSet);sptSet[u] true;for (int v 0; v V; v) {if (!sptSet[v] graph[u][v] ! 0 dist[u] ! Integer.MAX_VALUE dist[u] graph[u][v] dist[v]) {dist[v] dist[u] graph[u][v];}}}return dist;}private static int minDistance(int[] dist, boolean[] sptSet) {int min Integer.MAX_VALUE, minIndex -1;for (int v 0; v dist.length; v) {if (!sptSet[v] dist[v] min) {min dist[v];minIndex v;}}return minIndex;}}八、设计模式在算法中的应用8.1 策略模式实现排序算法// 策略接口interface SortStrategy {void sort(int[] array);}// 具体策略class BubbleSortStrategy implements SortStrategy {Overridepublic void sort(int[] array) {// 冒泡排序实现for (int i 0; i array.length - 1; i) {for (int j 0; j array.length - i - 1; j) {if (array[j] array[j 1]) {int temp array[j];array[j] array[j 1];array[j 1] temp;}}}}}class QuickSortStrategy implements SortStrategy {Overridepublic void sort(int[] array) {quickSort(array, 0, array.length - 1);}private void quickSort(int[] array, int low, int high) {if (low high) {int pi partition(array, low, high);quickSort(array, low, pi - 1);quickSort(array, pi 1, high);}}private int partition(int[] array, int low, int high) {int pivot array[high];int i low - 1;for (int j low; j high; j) {if (array[j] pivot) {i;swap(array, i, j);}}swap(array, i 1, high);return i 1;}private void swap(int[] array, int i, int j) {int temp array[i];array[i] array[j];array[j] temp;}}// 上下文类class Sorter {private SortStrategy strategy;public Sorter(SortStrategy strategy) {this.strategy strategy;}public void setStrategy(SortStrategy strategy) {this.strategy strategy;}public void sort(int[] array) {strategy.sort(array);}}// 使用示例public class StrategyPatternDemo {public static void main(String[] args) {int[] array {5, 2, 8, 1, 9, 3};Sorter sorter new Sorter(new BubbleSortStrategy());sorter.sort(array);System.out.println(Bubble sort: Arrays.toString(array));sorter.setStrategy(new QuickSortStrategy());sorter.sort(array);System.out.println(Quick sort: Arrays.toString(array));}}Java算法生态的丰富性使得开发者可以根据具体场景选择最合适的工具。从传统的集合框架到现代的Stream API从单线程算法到并发编程Java提供了完整的算法工具箱。掌握这些算法不仅能够提高代码效率还能写出更优雅、更易维护的程序。如果您喜欢此文章请收藏、点赞、评论谢谢祝您快乐每一天。