java面试上机题

### Java 编程语言面试上机练习题 以下是关于Java编程语言的一些常见面试上机练习题，涵盖了基础语法、字符串处理、集合框架以及多线程等内容： #### 字符串比较 ```java public class Test { public static void main(String[] args) { String s1 = "HelloWorld"; String s2 = new String("HelloWorld"); if (s1 == s2) { System.out.println("s1 == s2"); } else { System.out.println("s1 != s2"); } if (s1.equals(s2)) { System.out.println("s1 equals s2"); } else { System.out.println("s1 not equals s2"); } } } ``` 上述代码的输出结果为 `s1 != s2` 和 `s1 equals s2`[^4]。 #### 数组操作 编写一个方法来反转整型数组中的元素顺序并返回新的数组。例如输入 `[1, 2, 3, 4]` 输出应为 `[4, 3, 2, 1]`。 ```java public int[] reverseArray(int[] array) { int n = array.length; int[] reversed = new int[n]; for (int i = 0; i < n; i++) { reversed[i] = array[n - 1 - i]; } return reversed; } ``` #### 多线程实现 创建两个线程分别打印奇数和偶数，要求按照顺序依次打印出来，比如先打印1再打印2以此类推直到指定的最大数值为止。 ```java class OddEvenPrinter { private boolean isOddTurn = true; synchronized void printOdd(int number) throws InterruptedException { while (!isOddTurn) wait(); System.out.print(number + " "); isOddTurn = false; notifyAll(); } synchronized void printEven(int number) throws InterruptedException { while (isOddTurn) wait(); System.out.print(number + " "); isOddTurn = true; notifyAll(); } } public class ThreadExample { public static void main(String[] args) { final OddEvenPrinter printer = new OddEvenPrinter(); Runnable oddTask = () -> { try { for (int i = 1; i <= 100; i += 2) { printer.printOdd(i); } } catch (InterruptedException e) {} }; Runnable evenTask = () -> { try { for (int i = 2; i <= 100; i += 2) { printer.printEven(i); } } catch (InterruptedException e) {} }; new Thread(oddTask).start(); new Thread(evenTask).start(); } } ``` #### 集合框架应用 给定一组单词列表，请统计每个单词出现的次数并将结果存储到Map中。 ```java import java.util.*; public class WordCount { public Map<String, Integer> countWords(List<String> words) { Map<String, Integer> wordCounts = new HashMap<>(); for (String word : words) { wordCounts.put(word, wordCounts.getOrDefault(word, 0) + 1); } return wordCounts; } } ```