1.Java 创建自定义类数组方法 ：
Student [] stu = neuer Schüler [3]; für (int i = 0; i <3; i ++) {stu [i] = new Student ();｝2. 否则会提示空指针异常
Paketprojekt; Java.io importieren. privater Zeichenfolge Name; Privat int Score; public void setId (int id) {this.id = id; } public int getid () {return this.id; } public void setName (String -Name) {this.name = name; } public String getName () {return this.name; } public void setScore (int Score) {this.score = Score; } public int getCore () {return this.score; }} public class Project2 {Datei Datei = neue Datei ("e: /data.txt"); FileWriter FileWrite = NULL; BufferedWriter write = null; FileReader fileRead = null; BufferedReader read = null; Student [] stu = neuer Schüler [3]; public void put () {try {filewrite = new FileWriter (Datei); } catch (ioException e) {// todo 自动生成的 catch 块 e.printstacktrace (); } write = new bufferedWriter (FileWrite); für (int i = 0; i <3; i ++) {System.out.println ("请输入第" + (i + 1) + "个学生的 id, 姓名, 成绩:"); Scanner in = neuer Scanner (System.in); try {string str = in.nextline (); String Data [] = str.split (""); für (int j = 0; j <3; j ++) {write.write (data [j]); write.newline (); }} catch (ioException e) {// Todo 自动生成的 catch 块 e.printstacktrace (); }} try {write.close (); filewrite.close (); } catch (ioException e) {// todo 自动生成的 catch 块 e.printstacktrace (); }} public void get () {int sum = 0; Double Ave; try {fileRead = new FileReäen (Datei); } catch (FilenotFoundException e) {// Todo 自动生成的 catch 块 e.printstacktrace (); } read = new bufferedReader (fileRead); für (int i = 0; i <3; i ++) {stu [i] = new Student (); try {stu [i] .setId (Integer.ParseInt (read.Readline ())); stu [i] .setName (read.readline ()); stu [i] .setScore (Integer.ParseInt (read.Readline ())); } catch (Ausnahme e) {// todo 自动生成的 catch 块 e.printstacktrace (); }} für (int i = 0; i <3; i ++) {sum += stu [i] .getScore (); } ave = sum * 1.0/3; System.out.println ("学生的平均成绩为 ：" + Ave); try {read.close (); fileRead.close (); } catch (ioException e) {// todo 自动生成的 catch 块 e.printstacktrace (); }} public static void main (String [] args) {project2 pro = new Project2 (); pro.put (); pro.get (); }}总结 ：
这样我们就可以在项目当中, 根据项目需求自己来定义想要的数组.