Java 面试题代码指南216

在竞争激烈的 Java 市场中，掌握必要的编码技能对于成功的面试至关重要。本文提供了一个全面的代码指南，涵盖 Java 面试中常见的编程问题，旨在帮助候选人有效地准备和展示他们的 Java 编程能力。

核心 Java 概念

1. 创建和初始化一个 Java 对象：
```java
public class Employee {
private String name;
private int age;
public Employee(String name, int age) {
= name;
= age;
}
}
Employee employee = new Employee("John Doe", 30);
```
2. 重写 equals() 和 hashCode() 方法：
```java
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != ()) return false;
Employee employee = (Employee) o;
return (name, ) && age == ;
}
@Override
public int hashCode() {
return (name, age);
}
```
3. 实现 Comparable 接口：
```java
public class Employee implements Comparable {
private String name;
private int age;
@Override
public int compareTo(Employee other) {
return ();
}
}
```

数据结构和算法

4. 实现一个栈：
```java
public class Stack {
private List elements;
public Stack() {
elements = new ArrayList();
}
public void push(T element) {
(element);
}
public T pop() {
if (()) {
throw new EmptyStackException();
}
return (() - 1);
}
}
```
5. 实现一个队列：
```java
public class Queue {
private List elements;
public Queue() {
elements = new ArrayList();
}
public void enqueue(T element) {
(element);
}
public T dequeue() {
if (()) {
throw new EmptyQueueException();
}
return (0);
}
}
```
6. 线性搜索：
```java
public static int linearSearch(T[] array, T element) {
for (int i = 0; i < ; i++) {
if (array[i].equals(element)) {
return i;
}
}
return -1;
}
```

面向对象设计

7. 创建一个抽象类并实现其子类：
```java
public abstract class Shape {
protected String color;
public Shape(String color) {
= color;
}
public abstract double getArea();
}
public class Rectangle extends Shape {
private double width;
private double height;
public Rectangle(String color, double width, double height) {
super(color);
= width;
= height;
}
@Override
public double getArea() {
return width * height;
}
}
```
8. 实现接口：
```java
public interface Animal {
void makeSound();
}
public class Dog implements Animal {
@Override
public void makeSound() {
("Woof!");
}
}
```
9. 多态性：
```java
public class Animal {
public void makeSound() {
("Animal sound");
}
}
public class Dog extends Animal {
@Override
public void makeSound() {
("Woof!");
}
}
public class Cat extends Animal {
@Override
public void makeSound() {
("Meow!");
}
}
public class Main {
public static void main(String[] args) {
Animal animal = new Dog();
(); // Output: Woof!
animal = new Cat();
(); // Output: Meow!
}
}
```

异常处理

10. 抛出和处理异常：
```java
public void validateAge(int age) throws IllegalArgumentException {
if (age < 0) {
throw new IllegalArgumentException("Age cannot be negative");
}
}
public void main() {
try {
validateAge(-1);
} catch (IllegalArgumentException e) {
(()); // Output: Age cannot be negative
}
}
```
11. 创建自定义异常：
```java
public class MyException extends Exception {
public MyException(String message) {
super(message);
}
}
public void validateAge(int age) throws MyException {
if (age < 0) {
throw new MyException("Age cannot be negative");
}
}
```

Java 8+ 特性

12. Lambda 表达式：
```java
List numbers = (1, 2, 3, 4, 5);
((Integer number) -> (number));
```
13. 流处理：
```java
List numbers = (1, 2, 3, 4, 5);
int sum = ()
.filter(n -> n % 2 == 0)
.reduce(0, Integer::sum);
```
14. Optional：
```java
Optional name = ("John Doe");
if (()) {
(()); // Output: John Doe
}
```