1.java创建自定义类数组方法:
Student [] Stu = new Student [3]; for(int i = 0; i <3; i ++){stu [i] = new Student();2.否则会提示空指针异常
パッケージプロジェクト。 Import Java.io。プライベート文字列名;プライベートINTスコア。 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スコア){this.score = score; } public int getScore(){return this.score; }} public class project2 {file file = new file( "e:/data.txt"); filewriter filewrite = null; bufferedwriter write = null; filreader fileRead = null; BufferedReader read = null;学生[] stu = new Student [3]; public void put(){try {filewrite = new filewriter(file); } catch(ioexception e){// todo } write = new BufferedWriter(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:");スキャナーin = new Scanner(system.in); try {string str = in.nextline(); string data [] = str.split( ""); for(int j = 0; j <3; j ++){write.write(data [j]); write.newline(); }} catch(ioexception e){// todo }} try {write.close(); filewrite.close(); } catch(ioexception e){// todo }} public void get(){int sum = 0;ダブルアベニュー; try {fileRead = new fileReader(file); } catch(filenotfoundexception e){// todo } read = new BufferedReader(fileread); for(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(Exception E){// todo }} for(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 }} 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。