1.Java 创建自定义类数组方法:
Aluno [] stu = novo aluno [3]; para (int i = 0; i <3; i ++) {stu [i] = new Student ();｝2. 否则会提示空指针异常
projeto de pacote; importar java.io.*; importar java.util.scanner; classe de classe {private int id; nome de string privado; Pontuação privada int; public void setId (int id) {this.id = id; } public int getId () {return this.id; } public void setName (nome da string) {this.name = name; } public string getName () {return this.name; } public void SetScore (Int Score) {this.score = score; } public int getScore () {return this.score; }} classe pública Project2 {arquivo file = new File ("e: /data.txt"); FileWriter fileWrite = null; Bufferwriter write = null; Filereader fileread = null; BufferredReader read = null; Aluno [] Stu = novo aluno [3]; public void put () {try {fileWrite = new FileWriter (arquivo); } catch (ioexception e) {// TODO 自动生成的 Catch 块 E.PrintStackTrace (); } write = new BufferWriter (FileWrite); for (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 = new Scanner (System.in); tente {string str = in.NextLine (); String data [] = str.split (""); for (int j = 0; j <3; j ++) {write.write (dados [j]); write.newline (); }} catch (ioException e) {// TODO 自动生成的 Catch 块 E.PrintStackTrace (); }} tente {write.close (); fileWrite.close (); } catch (ioexception e) {// TODO 自动生成的 Catch 块 E.PrintStackTrace (); }} public void get () {int sum = 0; dupla ave; tente {fileRead = new FileReader (arquivo); } catch (filenotfoundException e) {// TODO 自动生成的 Catch 块 E.PrintStackTrace (); } read = new BufferredReader (fileRead); for (int i = 0; i <3; i ++) {stu [i] = new Student (); tente {stu [i] .setId (Integer.parseint (read.readline ())); stu [i] .setName (read.readline ()); Stu [i] .SetSCore (Integer.parseint (read.readline ())); } catch (Exceção e) {// TODO 自动生成的 Catch 块 E.PrintStackTrace (); }} para (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); tente {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.