Java Comparator compareToIgnoreCase

Question

我试图使用compareToIgnoreCase对字符串数组进行排序.
该字符串包含名称ex:Billy Jean
当我尝试比较它们时,我得到一个空指针异常.我认为这是因为名字和姓氏之间的空格.我如何比较全名？

谢谢

 class CompareStudentNames implements Comparator{

 //Sorts the students by name ignoring case.
@Override
public int compare(Object o1, Object o2) {
    String name1 = ((Student)o1).getName();
    String name2 = ((Student)o2).getName();

return (name1.compareToIgnoreCase(name2));

}

}

编辑---在使用比较学生姓名的代码中添加

private static void newInputFileReading(File f) throws FileNotFoundException{
    String inputLine = null;
    String [] inputSplit = new String[7];
    Boolean proceed = false;
    Scanner enterReader = new Scanner(System.in);
    String name;
        while(!proceed){            
            int stunum = -1;
            try {                   

                Scanner inputReader = new Scanner(f);

                while(inputReader.hasNextLine()){


                    studentNM.add(new Student());
                    ++stunum;
                    inputLine = inputReader.nextLine();
                    inputSplit = inputLine.split(",");
                    testForWord(inputSplit);
                    System.out.println(inputSplit[0]);
                    name = inputSplit[0];
                    System.out.println(name);
                    for(int i = 1; i<8; i++){
                        if(i == 0){
                            studentNM.get(stunum).setName(name);
                        }// where to send the name on run 0                         
                        else if(i <= 4 && i>0){
                            studentNM.get(stunum).setQuiz(testForDouble(inputSplit,i), i-1);
                        }// where to output to runs 1-4
                        else if(i>4 && i <= 6){
                            studentNM.get(stunum).setMids(testForDouble(inputSplit,i),i-5);
                        }// where to output on runs 5 & 6
                        else if( i> 6){
                            studentNM.get(stunum).setFinal(testForDouble(inputSplit,i));
                        }// where to output on the 7th run                          
                    }// for loop to  assign the inputs                      
                }// while scanner has next
                proceed = true;             
                Collections.sort(studentNM, new CompareStudentNames());


            }//try to initalize a new scanner and get & assign the inputs

            catch (FileNotFoundException e) {
                proceed = false;
                studentNM.clear();
                System.out.println("The file appears to have gone missing, please restart the program");
                System.out.println("Press Enter to continue");
                enterReader.nextLine();
                System.out.println("");
            }// catch a file not found exception
            catch(formatError | NumberFormatException e){
                proceed = false;
                studentNM.clear();
                System.out.printf("You input file is formatted incorrectly\nEvery line must start with a word,followed by 7 numbers, seperated by commas.\nPlease reformat your file and try again.\n");
                System.out.println("Press Enter to continue");
                enterReader.nextLine();
                System.out.println("");
            }// catch format error
            catch (Exception e) {
                proceed = false;
                studentNM.clear();
                System.out.println("An unknown error occured, please restart the program");
                e.printStackTrace();
                System.out.println("Press Enter to continue");
                enterReader.nextLine();
                System.out.println("");
            }

        }// while to make sure the first token is a word

}// newInputFileReading

我不认为Student对象得到的名字是因为

System.out.println(studentNM.get(0).getName());

显示null;

Answer 1

您应该向学生输入您的Comoarator,即Comparator<Student>:

class CompareStudentNames implements Comparator<Student> {

//Sorts the students by name ignoring case.
@Override
public int compare(Student o1, Student o2) {
    String name1 = o1.getName();
    String name2 = o2.getName();

    return name1.compareToIgnoreCase(name2);
}

另外,你应该检查:

• 你没有排序空值 - 尤其是(未初始化的)数组/数组元素的问题
• 学生们都有(非空)名字