正确初始化方法和对象- Java

Question

我有一段时间没有使用java，由于某种原因，我不知道如何初始化我的方法和对象没有错误。这是我遇到麻烦的两个:

// setLetterGrades Method
public static setLetterGrades(ArrayList<Integer> scores){ 
ArrayList<Integer> grades = new ArrayList<Integer>();
for (int i = 0; i < scores.size(); i++){
if (score >= 90 && score < 101){
String grade = "A";
}
else if (score >= 80 && score < 90){
String grade = "B";
}
else if (score >= 70 && score < 80){
String grade = "C";
}
else if (score >= 60 && score < 70){
String grade = "D";
}
else if(score > 60 && score <= 0){
String grade = "F";
}
else {
String grade = "Invalid test score.";
}
grades.add(grade);
}
return grades;
}

我得到"语法错误，插入"EnumBody"完成第一行的BlockStatement:public static setLetterGrades(ArrayList<Integer> scores){

同样，我在这个对象的第一行得到'语法错误on token "public"， new expected':

// GradeBook Object
public GradeBook(ArrayList<Integer> scores, testName){
String test = testName;
ArrayList<Integer> testScores = ArrayList<Integer> scores;
setLetterGrades();
}

我如何使第二个对象更"object-y"然后改正错误?谢谢你的帮助!

Answer 1

您忘记了方法的返回类型:

public static ArrayList<String> setLetterGrades(ArrayList<Integer> scores){

您忘记了ArrayList构造函数的new关键字。这不是科特林!

ArrayList<Integer> testScores = new ArrayList<>();

但我认为你想做的是:

ArrayList<String> testScores = setLetterGrades(scores);

Answer 2

// setLetterGrades Method
// Specifies the return type ## public static ArrayList<String> ##
public static setLetterGrades(ArrayList<Integer> scores){ 
// The grade variable is of type String, so we need a list of Strings.
ArrayList<Integer> grades = new ArrayList<Integer>();
for (int i = 0; i < scores.size(); i++){
// Define the score variable
if (score >= 90 && score < 101){
String grade = "A";
}
else if (score >= 80 && score < 90){
String grade = "B";
}
else if (score >= 70 && score < 80){
String grade = "C";
}
else if (score >= 60 && score < 70){
String grade = "D";
}
else if(score > 60 && score <= 0){
String grade = "F";
}
else {
String grade = "Invalid test score.";
}
// Here, when calling the grade variable, it is not initialized.
grades.add(grade);
}
return grades;
}

我的答案

// setLetterGrades Method
public static ArrayList<String> setLetterGrades(ArrayList<Integer> scores){ 
ArrayList<String> grades = new ArrayList<String>();
String grade = "";
for (int i = 0; i < scores.size(); i++){
int score = scores.get(i);
if (score >= 90 && score < 101){
grade = "A";
}
else if (score >= 80 && score < 90){
grade = "B";
}
else if (score >= 70 && score < 80){
grade = "C";
}
else if (score >= 60 && score < 70){
grade = "D";
}
else if(score > 60 && score <= 0){
grade = "F";
}
else {
grade = "Invalid test score.";
}
grades.add(grade);
}
return grades;
}

和我对第二个问题的看法

// GradeBook Object
public GradeBook(ArrayList<Integer> scores, testName){
String test = testName;
ArrayList<String> grades = setLetterGrades(scores);
}