1.定義回撥函式介面

裡面包含一個方法

public interface CallBack {
	
	public void execute();

}

2.定義回撥函式的實現 

public class BookCallBack implements CallBack{

	private String bookName;  	
	 private String author;
	 
	public String getBookName() {
		return bookName;
	}
	public void setBookName(String bookName) {
		this.bookName = bookName;
	}
	public String getAuthor() {
		return author;
	}
	public void setAuthor(String author) {
		this.author = author;
	}

	@Override
	public void execute() {
		this.bookName = "The little prince";
		this.author = "Antoine";
 		System.out.println("---------callback實現類 bookName=="+ this.bookName +"      author==="+this.author);
	}

}
 

3.定義業務處理類

業務處理類裡的方法形參傳入CallBack介面。

業務處理類裡的方法內容包括：處理業務和執行回撥函式。

//業務處理類
public class TestBookCallBack {
	
	public void test(CallBack callBack){
		
		//1.處理業務
		System.out.println("---------業務處理類 TestBookCallBack---------");
		//2.執行回撥函式
		callBack.execute(); 
	}

}

4.1 定義主函式-使用匿名內部類 實現callback

import org.junit.Test;

public class Main {

	@Test
	public void main() {

		TestBookCallBack testBookCallBack = new TestBookCallBack();
		testBookCallBack.test(new CallBack() {
			@Override
			public void execute() {
				System.out.println("-------------------Anonymous Inner Class-------------------");
			}
		});
	}

}
 

 執行結果為

---------業務處理類 TestBookCallBack---------
---------Anonymous Inner Class--------- 

4.2定義主函式，使用callback的實現類 實現callback

import org.junit.Test;

public class Main {
 
	@Test
	public void main() {

		TestBookCallBack testBookCallBack = new TestBookCallBack();
		BookCallBack bookCallBack = new BookCallBack();
		testBookCallBack.test(bookCallBack);
		System.out.println("---------main---------在主函式中 獲取callback實現類裡定義的變數值----------" + bookCallBack.getBookName()+"----"+ bookCallBack.getAuthor());

	}
 
}
 

執行結果

---------業務處理類 TestBookCallBack---------
---------callback實現類 bookName==The little prince      author===Antoine
---------main---------在主函式中 獲取callback實現類裡定義的變數值----------The little prince----Antoine