​​1. 接口的定义与实现​​

​​(1) 定义接口​​

// 定义一个 "动物行为" 的接口
public interface Animal {void eat();      // 抽象方法（无实现）void sleep();    // 抽象方法（无实现）// Java 8+ 默认方法（有实现）default void breathe() {System.out.println("呼吸空气");}// Java 8+ 静态方法static boolean isAnimal(Object obj) {return obj instanceof Animal;}
}

​​(2) 实现接口​​

// Dog 类实现 Animal 接口
public class Dog implements Animal {@Overridepublic void eat() {System.out.println("狗吃狗粮");}@Overridepublic void sleep() {System.out.println("狗在窝里睡觉");}
}

​​(3) 使用接口​​

Animal myDog = new Dog();
myDog.eat();    // 输出: 狗吃狗粮
myDog.breathe(); // 输出: 呼吸空气（调用默认方法）
Animal.isAnimal(myDog); // true（调用静态方法）

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文件结构​

src/
└── com/└── example/└── workflow/├── ExecutorCallback.java├── MyCallback.java├── WorkflowExecutor.java└── Main.java

1. ExecutorCallback.java​​

package com.example.workflow;// 定义回调接口，无需额外导入
public interface ExecutorCallback {void onStart();void onStepDone(String step);void onComplete();void onError(String error);
}

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​​2. MyCallback.java​​

package com.example.workflow;// 需要导入同一包内的接口
import com.example.workflow.ExecutorCallback;public class MyCallback implements ExecutorCallback {@Overridepublic void onStart() {System.out.println("工作流开始执行！");}@Overridepublic void onStepDone(String step) {System.out.println("步骤完成: " + step);}@Overridepublic void onComplete() {System.out.println("✅ 全部执行完毕！");}@Overridepublic void onError(String error) {System.out.println("❌ 错误: " + error);}
}

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​​3. WorkflowExecutor.java​​

package com.example.workflow;// 导入同一包内的接口
import com.example.workflow.ExecutorCallback;public class WorkflowExecutor {private ExecutorCallback callback;public void setCallback(ExecutorCallback callback) {this.callback = callback;}public void execute() {try {callback.onStart();callback.onStepDone("步骤1");Thread.sleep(1000); // 属于 java.lang，无需显式导入callback.onStepDone("步骤2");Thread.sleep(1000);callback.onComplete();} catch (InterruptedException e) {callback.onError("执行超时");}}
}

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​​4. Main.java​

package com.example.workflow;// 导入同一包内的类
import com.example.workflow.WorkflowExecutor;
import com.example.workflow.MyCallback;public class Main {public static void main(String[] args) {WorkflowExecutor executor = new WorkflowExecutor();executor.setCallback(new MyCallback());executor.execute();}
}

因为callback就是实例化的ExecutorCallback类了

callback.onStart() 等于 ExecutorCallback.onStart()