Java编程开发技巧:学习实用的代码技巧和设计模式

发布时间:2023-05-19

一、代码技巧

在Java开发中,有些代码技巧可以帮助我们更高效地完成工作。

1、使用Lambda表达式简化代码

public class Main {
   public static void main(String[] args) {
      List names = Arrays.asList("Tom", "Jerry", "Spike");

      names.forEach(name -> System.out.println(name));
   }
}

  

2、使用Optional类处理空指针异常

public class Main {
   public static void main(String[] args) {
      String name = null;

      Optional optionalName = Optional.ofNullable(name);
      String realName = optionalName.orElse("unknown");

      System.out.println(realName);
   }
}

  

3、使用StringBuilder类构建字符串

public class Main {
   public static void main(String[] args) {
      StringBuilder stringBuilder = new StringBuilder();

      stringBuilder.append("Java");
      stringBuilder.append(" is");
      stringBuilder.append(" awesome!");

      System.out.println(stringBuilder.toString());
   }
}

二、设计模式

在Java开发中,设计模式可以帮助我们更好地组织代码。

1、单例模式

单例模式确保一个类只有一个实例,并提供全局访问点。

public class Singleton {
   private static Singleton instance;

   private Singleton() {}

   public static Singleton getInstance() {
      if (instance == null) {
         instance = new Singleton();
      }
      return instance;
   }
}

2、工厂模式

工厂模式用于生产对象,而不需要直接调用构造函数。

public interface Shape {
   void draw();
}

public class Circle implements Shape {
   @Override
   public void draw() {
      System.out.println("Circle::draw()");
   }
}

public class Rectangle implements Shape {
   @Override
   public void draw() {
      System.out.println("Rectangle::draw()");
   }
}

public class ShapeFactory {
   public static Shape getShape(String shapeType) {
      if (shapeType.equalsIgnoreCase("CIRCLE")) {
         return new Circle();
      } else if (shapeType.equalsIgnoreCase("RECTANGLE")) {
         return new Rectangle();
      }
      return null;
   }
}

3、观察者模式

观察者模式定义了对象间的一对多关系,使得当一个对象状态改变时,所有依赖于它的对象都会被通知并自动更新。

public interface Observer {
   void update();
}

public class Subject {
   private List observers = new ArrayList<>();
   private int state;

   public int getState() {
      return state;
   }

   public void setState(int state) {
      this.state = state;
      notifyAllObservers();
   }

   public void attach(Observer observer) {
      observers.add(observer);
   }

   public void notifyAllObservers() {
      for (Observer observer : observers) {
         observer.update();
      }
   }
}

public class BinaryObserver implements Observer {
   private Subject subject;

   public BinaryObserver(Subject subject) {
      this.subject = subject;
      this.subject.attach(this);
   }

   @Override
   public void update() {
      System.out.println("Binary String: " + Integer.toBinaryString(subject.getState()));
   }
}

public class OctalObserver implements Observer {
   private Subject subject;

   public OctalObserver(Subject subject) {
      this.subject = subject;
      this.subject.attach(this);
   }

   @Override
   public void update() {
      System.out.println("Octal String: " + Integer.toOctalString(subject.getState()));
   }
}

public class Main {
   public static void main(String[] args) {
      Subject subject = new Subject();
      new BinaryObserver(subject);
      new OctalObserver(subject);

      System.out.println("First state change: 15");
      subject.setState(15);

      System.out.println("Second state change: 10");
      subject.setState(10);
   }
}

  

三、总结

Java编程开发技巧和设计模式在Java开发中非常重要。掌握这些知识可以使我们成为更优秀的Java开发者。