Java技术指南：从基础到高级的全面概览
导读：Java是一种广泛使用的编程语言，具有跨平台、面向对象和强大的生态系统等诸多优势。本文将从基础到高级逐步介绍Java的核心概念和主要技术，并提供具体的代码示例，帮助读者快速入门并深入理解Java编程。
第一部分：Java基础知识
int age = 25;
double price = 12.5;
char grade = 'A';
boolean isValid = true;
String name = "John";
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if (score >= 90) {
System.out.println("优秀");
} else if (score >= 80) {
System.out.println("良好");
} else {
System.out.println("及格");
}
for (int i = 0; i 0) {
System.out.println(count);
count--;
}
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int[] numbers = new int[5];
numbers[0] = 1;
numbers[1] = 2;
numbers[2] = 3;
numbers[3] = 4;
numbers[4] = 5;
String[] names = {"Alice", "Bob", "Charlie"};
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第二部分：面向对象编程
public class Person {
private String name;
private int age;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public void sayHello() {
System.out.println("Hello, my name is " + name);
}
}
Person person = new Person("John", 25);
person.sayHello();
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public class Animal {
public void makeSound() {
System.out.println("Animal makes sound");
}
}
public class Cat extends Animal {
@Override
public void makeSound() {
System.out.println("Cat says Meow");
}
}
Animal animal = new Cat();
animal.makeSound();
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public interface Drawable {
void draw();
}
public abstract class Shape implements Drawable {
protected int x;
protected int y;
public Shape(int x, int y) {
this.x = x;
this.y = y;
}
@Override
public void draw() {
System.out.println("Drawing shape at (" + x + ", " + y + ")");
}
public abstract double area();
}
public class Circle extends Shape {
private double radius;
public Circle(int x, int y, double radius) {
super(x, y);
this.radius = radius;
}
@Override
public double area() {
return Math.PI * radius * radius;
}
}
Shape shape = new Circle(0, 0, 5);
shape.draw();
System.out.println("Area: " + shape.area());
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第三部分：Java高级特性
try {
int result = divide(10, 0);
System.out.println(result);
} catch (ArithmeticException e) {
System.out.println("Error: " + e.getMessage());
}
public int divide(int num1, int num2) {
if (num2 == 0) {
throw new ArithmeticException("Divisor cannot be zero");
}
return num1 / num2;
}
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try (BufferedReader reader = new BufferedReader(new FileReader("file.txt"))) {
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
System.out.println("Error: " + e.getMessage());
}
try (BufferedWriter writer = new BufferedWriter(new FileWriter("file.txt"))) {
writer.write("Hello, World!");
} catch (IOException e) {
System.out.println("Error: " + e.getMessage());
}
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public class MyThread extends Thread {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
System.out.println(Thread.currentThread().getName() + ": " + i);
}
}
}
MyThread thread1 = new MyThread();
MyThread thread2 = new MyThread();
thread1.start();
thread2.start();
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结语：本文从Java基础知识、面向对象编程到Java高级特性，对Java技术进行了全面概览，并提供了具体的代码示例。希望本文能帮助读者快速入门并深入理解Java编程，为进一步学习Java打下良好基础。
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