首先，参考一下众多文章中，把接口回调讲得比较浅显易懂的两篇文章：

举个例子

网友提供的一些例子，虽然接地气，但是，不够专业，还是欣叔的例子好一些，把代码取出来，原理讲解移步<码农翻身>公众号。

public class XiaoZhang implements IFileIoCallback {        public void saveStr(){        String fileName = "callback.txt";        String str = "this is a callback demo.";        FileIO fileIO = new FileIO();        fileIO.saveStrToFile(fileName,str,this);    }    @Override    public void onResult(boolean isSave) {        System.out.println(isSave ? "success" : "fail" );    }}

public class FileIO {    public void saveStrToFile(String fileName, String content, final IFileIoCallback callback){        new Thread(new Runnable() {            @Override            public void run() {                try {                    //write str to file...                    callback.onResult(true);                }catch (Exception e){                    e.printStackTrace();                    callback.onResult(false);                }            }        }).start();    }}

public interface IFileIoCallback {    void onResult(boolean isSave);}