我要评论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
package project;
import java.io.*;
import java.util.scanner;
class student
{
private int id;
private string name;
private 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 getscore()
{
return this.score;
}
}
public class project2 {
file file = new file("e:/data.txt");
filewriter filewrite = null;
bufferedwriter write = null;
filereader fileread = null;
bufferedreader read = null;
student []stu = new student[3];
public void put()
{
try {
filewrite = new filewriter(file);
} catch (ioexception e) {
// todo 自动生成的 catch 块
e.printstacktrace();
}
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:");
scanner 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 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 filereader(file);
} catch (filenotfoundexception e) {
// todo 自动生成的 catch 块
e.printstacktrace();
}
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 自动生成的 catch 块
e.printstacktrace();
}
}
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 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.
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