android中lambda运算符出错

我想使用lambda运算符使用Runnable方法编写代码，但我得到了一个错误 错误：（40，33）错误：lambda表达式在-source 1.7中不受支持 （使用-source 8或更高版本来启用lambda表达式） 这是我的密码：`

public void countDownStart(){
    handler= new Handler();
    runnable= (Runnable) () -> {
       handler.postDelayed((Runnable) this, 1000);
        try{
            SimpleDateFormat dateFormat= new SimpleDateFormat("YYYY-MM-DD");
            Date futureDate= dateFormat.parse("2017-03-31");
            Date currentDate= new Date();
            if (!currentDate.after(futureDate)){
                long diff = futureDate.getTime()- currentDate.getTime();
                long days = diff / (24 * 60 * 60 * 1000);
                diff -= days * (24 * 60 * 60 * 1000);
                long hours = diff / (60 * 60 * 1000);
                diff -= hours * (60 * 60 * 1000);
                long minutes = diff / (60 * 1000);
                diff -= minutes * (60* 1000);
                long seconds = diff / 1000;
             txtTimerDay.setText("" + String.format("%02d", days));
             txtTimerHour.setText("" + String.format("%02d", hours));
             txtTimerMinute.setText("" + String.format("%02d", minutes));
             txtTimerSecond.setText("" + String.format("%02d", seconds));
            }else{
                tvEvent.setVisibility(View.VISIBLE);
                tvEvent.setText("The Event Started");
                textViewGone();
            }
        } catch (Exception e){
            e.printStackTrace();
        }
    };
    handler.postDelayed(runnable, 1 * 1000);
}

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您是否在build.gradle文件中添加了以下说明

defaultConfig {

    jackOptions {
      enabled true
    }
  }
  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }

---

您正在使用Java7。自Java8以来，lambda表达式一直受支持。android的问题是，只有android n（7.0）或更高版本支持Java8。如果您仍然希望在较低的android版本中使用lambdas，可以使用类似的库，但这些库通常不支持java lambdas的所有功能

你的JAVA verson是什么？你在谷歌上搜索过错误信息吗？