为什么我的文本文件在 Java Eclipse 中没有作为字符串读取?

Why isn't my text file reading in Java Eclipse as a String?

我是 Java Eclipse 的初学者。我正在尝试读取 .txt 文件,并将数据用作字符串值。但是,当我使用 if 语句时,条件不是将值注册为字符串,因此不满足任何条件,我只得到最终的 else.

我的代码的目的是读取文本文件并确定所需的值:即如果该行以“avg”开头,程序必须显示以下数字的平均值。

我的 .txt 文件内容是这样的:

分:1,2,3,4,5,6\n max:1,2,3,4,5,6\n avg:1,2,3,4,5,6

这是我的部分代码:

public static void main(String[] args) throws IOException {
    
    //declare variables
    String line, operation;
    int min, max, sum, num;
    double avg;
    List<String> lineArray;
    String outputPath = "C:\output.txt";       //these are not the actual file paths, i just didnt 
    String inputPath = "C:\input.txt";         //want to give personal information.

    //try open file
    try {
        
        //create File instance  
        File text = new File (inputPath);   
        Scanner scnr = new Scanner(text);                               

        //loop until end of text file
        while ( scnr.hasNextLine() ) {
                            
            line = scnr.nextLine();                  //read line from text file
            operation = line.substring(0,3);         //get operation from String data
            
            line = line.substring(4);                //get String value of numbers              
            lineArray = Arrays.asList(line.split(","));     //separate string into array elements

            //setup initial values
            sum = 0;
            min = Integer.parseInt(lineArray.get(0));     //convert to Int
            max = Integer.parseInt(lineArray.get(0));
            
            //loop through line array and determine min, sum and max of each
            for (int i = 0; i < lineArray.size(); i++ ) {
                
                num = Integer.parseInt(lineArray.get(i));
                sum += Integer.parseInt(lineArray.get(i));
                if (num > max)  max = num;
                if (num < max)  max = num;
                
            }
            
            avg = sum / lineArray.size();   
            
            //the IF condition statement that is not working                
            if (operation  == "min") {
                System.out.println(min);
            }
            
            else if (operation == "max") {
                System.out.println(max);
            }
            
            else if (operation == "avg") {
                System.out.println(avg);
            }
            
            else System.out.println("Error");
            
        }   //end of while loop
        
        scnr.close();                                                       //close scanner
        
    }   //end of try
    
    catch ( FileNotFoundException e ) {
    }
    
}   //end of "main" class

当我手动将操作设置为“min”或“max”或“avg”时,程序会正常运行。

您应该使用 operation.equals("min") 而不是操作 == "min"。以此类推其他字符串,你要比较。