空指针exeception处理程序 [英] Null Pointer exeception handler

问题描述

我已经做了这个功能FourActivity类：

 公众诠释getRandomNumber的（）{
    随机RND =新的随机（）;
    INT randomNumber = rnd.nextInt（100）;
    如果（randomNumber％2 == 1）{
        randomNumber = randomNumber + 1;
        返回randomNumber;    }    否则返回randomNumber;
}
 

我试图通过这样的方式在另一个类来访问此方法。但是，它抛出一个 显示java.lang.NullPointerException

  INT randomNumber;
FourActivity fourActivity;
randomNumber = fourActivity.getRandomNumber（）;Toast.makeText（FinalActivity.this，随机数+ randomNumber，Toast.LENGTH_SHORT）.show（）;
 

解决方案

请它

  INT randomNumber;
FourActivity fourActivity =新FourActivity（）;
randomNumber = fourActivity.getRandomNumber（）;Toast.makeText（FinalActivity.this，随机数+ randomNumber，Toast.LENGTH_SHORT）.show（）;
 

I have made a this function in FourActivity Class:

public int getRandomNumber(){
    Random rnd=new Random();
    int randomNumber=rnd.nextInt(100);


    if (randomNumber%2==1){
        randomNumber=randomNumber+1;
        return randomNumber;

    }

    else return randomNumber;
}

i am trying to Access this method in another class through this way. But it throws a java.lang.NullPointerException:

int randomNumber;
FourActivity fourActivity;
randomNumber= fourActivity.getRandomNumber();

Toast.makeText(FinalActivity.this,"Random Number is"+randomNumber ,Toast.LENGTH_SHORT).show();

解决方案

Make it

int randomNumber;
FourActivity fourActivity = new FourActivity();
randomNumber= fourActivity.getRandomNumber();

Toast.makeText(FinalActivity.this,"Random Number is"+randomNumber ,Toast.LENGTH_SHORT).show();

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