整個包的java變量

Question

我是Java的新手，我不知道如何制作它，因此if語句中的這兩個變量每次都需要更新。

public class Ex3 {

public static void main(String[] args) {
    //Here will display what pi is
    System.out.println("Pi in Netbeans Java is "+ Math.PI);

    //This will give how many numbers the for loops go up to
    int maxNum = 20;

    //This is for the subtraction parts of the equation
    for(int i = 1; i <= maxNum; i++){
        int subNum = 3;
        final double subCount = 1 - (1./(subNum + 4));
        subNum += 4;
    }
    for(int y = 1; y <= maxNum; y++){
        int addNum = 5;
        double addCount = 1 + (1./(addNum + 4));
        addNum += 4;
    }
}
double finalNum = subCount + addCount;
}

Answer 1

變量a僅限於在其中聲明的范圍，因此，如果在for塊中聲明變量，則只能在for塊中看到它們。

為了克服這個問題，請在使用main方法之前先聲明變量

public static void main(String[] args) {
  //Here will display what pi is
  System.out.println("Pi in Netbeans Java is "+ Math.PI);

  //This will give how many numbers the for loops go up to
  int maxNum = 20;
  double subCount = 0.0;
  double addCount = 0.0;
  int subNum = 3;
  int addNum = 5;

//This is for the subtraction parts of the equation
  for(int i = 1; i <= maxNum; i++){
    subCount = 1 - (1./(subNum + 4));
    // maybe should be
    // subCount += 1 - (1./(subNum + 4));
    subNum += 4;
  }
  for(int y = 1; y <= maxNum; y++){
    addCount = 1 + (1./(addNum + 4));
    // maybe should be
    // addCount += 1 + (1./(addNum + 4));
    addNum += 4;
  }

  System.out.println ("the result is " + (subCount + addCount));
}

編輯

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