1.java 创建自定义类数组方法 ：
Siswa [] Stu = Siswa Baru [3]; untuk (int i = 0; i <3; i ++) {Stu [i] = siswa baru ();｝2. 否则会提示空指针异常
proyek paket; impor java.io.*; import java.util.scanner; siswa kelas {private int id; nama string pribadi; skor int pribadi; public void setid (int id) {this.id = id; } public int getId () {return this.id; } public void setName (name string) {this.name = name; } public string getName () {return this.name; } public void setscore (skor int) {this.score = skor; } public int getScore () {return this.score; }} kelas publik Project2 {file file = file baru ("e: /data.txt"); FileWriter FileWrite = null; BufferedWriter write = null; Filereader fileread = null; BufferedReader baca = null; Siswa [] Stu = Siswa Baru [3]; public void put () {coba {fileWrite = new fileWriter (file); } catch (ioException e) {// todo 自动生成的 tangkap 块 e.printstacktrace (); } write = New BufferedWriter (FileWrite); untuk (int i = 0; i <3; i ++) {System.out.println ("请输入第" + (i + 1) + "个学生的 id, 姓名, 成绩:"); Pemindai di = pemindai baru (System.in); coba {string str = in.nextline (); String data [] = str.split (""); untuk (int j = 0; j <3; j ++) {write.write (data [j]); write.newline (); }} catch (ioException e) {// todo 自动生成的 tangkap 块 e.printstacktrace (); }} coba {write.close (); filewrite.close (); } catch (ioException e) {// todo 自动生成的 tangkap 块 e.printstacktrace (); }} public void get () {int sum = 0; Ave ganda; coba {fileread = new filereader (file); } catch (FileNotFoundException e) {// todo 自动生成的 tangkap 块 e.printstacktrace (); } baca = BufferedReader baru (FileRead); untuk (int i = 0; i <3; i ++) {stu [i] = siswa baru (); coba {stu [i] .setId (integer.parseint (read.readline ())); Stu [i] .setname (read.readline ()); Stu [i] .setscore (integer.parseint (read.readline ())); } catch (exception e) {// todo 自动生成的 tangkap 块 e.printstacktrace (); }} untuk (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); coba {baca.close (); fileread.close (); } catch (ioException e) {// todo 自动生成的 tangkap 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.