字符串中的正数和负数

Question

我必须制作一个程序，允许用户输入整数，直到按下“0”。程序必须打印：1）输入数字的总数2）正数3）正数的平均数4）负数5）负数的总和

到目前为止，我所能做的就是“输入直到按下‘0’”，并找到输入的数字的数量，这对我和我的编程技能来说是非常重要的。我很难找出这个数字是正数还是负数。也许我没有正确地比较他们，所以如果我能得到一些高级人员的帮助，我会很高兴。

这是我到目前为止的代码：

import java.io.*; 

class Nums { 
  public static void main(String args[])  
    throws IOException 
  { 
    BufferedReader br = new BufferedReader(new 
                            InputStreamReader(System.in)); 
    String str;
    int EnteredNumbers = -1;
    int Positive = 0;
    int Negative = 0;
    int NegativeSum = 0;
    double AveragePositive = 0;

    System.out.println("Enter '0' to quit."); 
    System.out.println("Enter Numbers: "); 
    do { 
      EnteredNumbers++;
      str = br.readLine();

    } while(!str.equals("0")); 
      System.out.println("You have have entered "+EnteredNumbers+ " numbers!");
      System.out.println("You have have entered "+Positive+ " Positive numbers!");
      System.out.println("The Average of the Positive Numebers is "+AveragePositive+ "!");
      System.out.println("You have have entered "+Negative+ " Negative numbers!");
      System.out.println("The Sum of the Negative numbers is "+NegativeSum+ "!");
  } 
}

Answer 1

希望下面的代码能达到你想要的效果

import java.io.*; 

class Nums { 
  public static void main(String args[])  
    throws IOException 
  { 
    BufferedReader br = new BufferedReader(new 
                            InputStreamReader(System.in)); 
    String str;
    int EnteredNumbers = -1;
    int Positive = 0;
    int Negative = 0;
    int NegativeSum = 0;
    double AveragePositive = 0;
    double PositiveSum = 0;

    System.out.println("Enter '0' to quit."); 
    System.out.println("Enter Numbers: "); 
    do { 
      EnteredNumbers++;
      str = br.readLine();
      if(Integer.parseInt(str) > 0){
          Positive++;
          PositiveSum = PositiveSum + Integer.parseInt(str);
          AveragePositive = PositiveSum/Positive;
      }
      if(Integer.parseInt(str) < 0){
          Negative++;
          NegativeSum = NegativeSum + Integer.parseInt(str);
      }

    } while(!str.equals("0")); 
      System.out.println("You have have entered "+EnteredNumbers+ " numbers!");
      System.out.println("You have have entered "+Positive+ " Positive numbers!");
      System.out.println("The Average of the Positive Numebers is "+AveragePositive+ "!");
      System.out.println("You have have entered "+Negative+ " Negative numbers!");
      System.out.println("The Sum of the Negative numbers is "+NegativeSum+ "!");
  } 
}

Answer 2

通过将字符串解析为int进行检查

Integer.parseInt(str)>0  //positive number
Integer.parseInt(str)<0 //negative



do { 
      EnteredNumbers++;
      str = br.readLine();
      int number= Integer.parseInt(str);
      if(number>0){  //do positive stuffs}
      else if(number<0){//do negative stuffs}
    } while(!str.equals("0")); 

Answer 3

首先，正如Integer.parseInt在java中用于从String转换为int。其次，您还需要有一个额外的变量来存储和累积正数的总数。我添加了一个try-cat异常块来处理错误。

这里有一个代码供参考。

import java.io.*; 

public class Nums { 
  public static void main(String args[])  
    throws IOException 
  { 
    BufferedReader br = new BufferedReader(new 
                            InputStreamReader(System.in)); 
    String str;
    int EnteredNumbers = -1;
    int Positive = 0;
    int Negative = 0;
    int NegativeSum = 0;
    int PositiveSum = 0; // Added extra variable
    double AveragePositive = 0;

    System.out.println("Enter '0' to quit."); 
    System.out.println("Enter Numbers: "); 
   try{
    do { 
      EnteredNumbers++;
      str = br.readLine();

    int num = Integer.parseInt(str);


    if (num>0)
      {
        Positive++;
        PositiveSum+=num;
      }
      else if (num<0)
      {
        Negative++;
        NegativeSum+=num;
      }
    } while(!str.equals("0")); 
    AveragePositive = (double)PositiveSum/(double)Positive;
      System.out.println("You have have entered "+EnteredNumbers+ " numbers!");
      System.out.println("You have have entered "+Positive+ " Positive numbers!");
      System.out.println("The Average of the Positive Numebers is "+AveragePositive+ "!");
      System.out.println("You have have entered "+Negative+ " Negative numbers!");
      System.out.println("The Sum of the Negative numbers is "+NegativeSum+ "!");
    }
    catch (java.lang.NumberFormatException e)
    {
        System.out.println("Wrong format");
    }  

} 
}

如果没有错误，则输出

Enter '0' to quit.
Enter Numbers: 
1
5
5
-5
-5
0
You have have entered 5 numbers!
You have have entered 3 Positive numbers!
The Average of the Positive Numebers is 3.6666666666666665!
You have have entered 2 Negative numbers!
The Sum of the Negative numbers is -10!