我正在创建一个应用程序，用于保存txt文件中游戏的用户名和分数。它的概念是，当它向txt文件写入新的用户名和分数时，它应该打开.txt文件，读取它然后复制它，在txt文件中添加一个新的uername和score条目。
我正在考虑使用2个对象数组。第一个是读入的，新的将是写入的，将再有一个条目。
因此，如果player[i]已重新player[i+1]，则应使用新条目进行写入。
我正在给你下面的代码！
private Player[] myplayer=null;
private Player[] mynewplayer=null;
//open Players.txt
int i;
int n;
String filename="players.txt";
try
{
FileReader fp=new FileReader(filename);
BufferedReader bf=new BufferedReader(fp);
n=Integer.parseInt(bf.readLine());
myplayer=new Player[n];
int x=n+1;
mynewplayer=new Player[x];
for(i=0;i<n;i++)
{
String s=bf.readLine();
String user="",score="";
user=s.substring(0,s.indexOf(","));
s=s.substring(s.indexOf(",")+1);
score=s;
myplayer[i]=new Player(user,Double.parseDouble(score));
for(i=0;i<n;i++)
{
mynewplayer[i]= myplayer[i];
}
mynewplayer[x]=new Player(Username,Double.parseDouble(score));
}
bf.close();
fp.close();
}catch(IOException e)
{
System.out.println("Exception was "+e.getMessage());
}
//----------------------------------WRITE mytxt!-------------
n=myplayer.length;
try
{
filename="players.txt";
FileWriter fp=new FileWriter(filename);
fp.write(""+n+"\n");
for(i=0;i<n+1;i++)
fp.write(""+mynewplayer[i]+"\n");
fp.close();
}catch(IOException e)
{
System.out.println("Exception was "+e.getMessage());
}
//----------------------------------WRITE mytxt!-----------
//Get on Message
String s="";
for(i=0;i<mynewplayer.length;i++)
s=s+mynewplayer[i]+"\n";
JOptionPane.showMessageDialog(null,"Players are \n "+s);
问题在于，当它被写入时，它会为null返回mynewplayer。
我想mynewplayer并没有真正接受“myplayer”的条目，但都没有写新的用户名。
编译不会显示任何错误。只需将NULL写入文本文件即可。
问我是否想要有关代码的更多信息！
提前致谢！
答案 0 :(得分：2)
以下是您的代码的编辑版本，有一些改进，应该对我更改的代码进行评论，解释我的所作所为。
Player[] myPlayer = null; // first word uncapitalized, every
Player[] myNewPlayer = null; // other word begins with a capital
//open Players.txt
int i, n; // combine the variables into 1 line
String filename = "players.txt";
try {
FileReader fp = new FileReader(filename);
BufferedReader bf = new BufferedReader(fp);
n = Integer.parseInt(bf.readLine());
// not needed
//myPlayer = new Player[n];
// NOT NEEDED int x = n + 1;
myNewPlayer = new Player[n + 1];
for (i = 0; i < n; i++) {
String s = bf.readLine();
String user, score; // combine variables, doesnt need to initalize them
String[] items = s.split(","); // Splits the line into array elements on every delimiter -> ,
//user = s.substring(0, s.indexOf(","));
//s = s.substring(s.indexOf(",") + 1);
//score = s;
user = items[0];
score = items[1];
// this line below isnt actually needed
//myPlayer[i] = new Player(user, Double.parseDouble(score));
// Create a new player clone, dont copy the previous one
myNewPlayer[i] = new Player(user, Double.parseDouble(score));
}
// We've read all the variables from the text file, now we create the last one
// Since myNewPlayer is (n+1) size, the range of the array is
// 0 to n
// the last index will be n New Score Variable
myNewPlayer[n] = new Player("Username variable", Double.parseDouble("22"));
bf.close();
fp.close();
} catch (IOException e) {
System.out.println("Exception was " + e.getMessage());
}
//----------------------------------WRITE mytxt!-------------
// This is called a ternary operator
// it is a 1 line if statement
// the format is like so
// booleanLogic ? trueAnswer Execution : falseAnswer Execution;
// if () { true }else { false }
n = myNewPlayer != null ? myNewPlayer.length : 0;
// CHANGED HERE - was using the first array rather than second
// dont need the 1st array
try {
filename = "players.txt";
FileWriter fp = new FileWriter(filename);
// Dont need "" before the items
fp.write(n + "\n");
for (i = 0; i < n; i++) {
fp.write(myNewPlayer[i] + "\n");
}
fp.close();
} catch (IOException e) {
System.out.println("Exception was " + e.getMessage());
}
//----------------------------------WRITE mytxt!-----------
//Get on Message
String s = "";
for (i = 0; i < myNewPlayer.length; i++) {
// s += ""; is like doing s = s + "";
s += myNewPlayer[i] + "\n";
}
JOptionPane.showMessageDialog(null, "Players are \n " + s);
答案 1 :(得分：1)
我相信你的问题是：
for(i=0;i<n;i++)
{
String s=bf.readLine();
String user="",score="";
user=s.substring(0,s.indexOf(","));
s=s.substring(s.indexOf(",")+1);
score=s;
myplayer[i]=new Player(user,Double.parseDouble(score));
for(i=0;i<n;i++)
{
mynewplayer[i]= myplayer[i];
}
mynewplayer[x]=new Player(Username,Double.parseDouble(score));
}
你有嵌套循环，这很好，但它们使用相同的计数器（变量i）。
所以发生的事情是读取文件的第一行，然后添加到myplayer [0]。但是，不是只将它添加到mynewplayer [0]，而是在i上启动另一个循环。这个循环：
for(i=0;i<n;i++)
{
mynewplayer[i]= myplayer[i];
}
将第一个播放器复制到mynewplayer [0] ...然后将null复制到其他所有条目中（因为myplayer只填充了firsdt元素）。 问题是在循环完成后，我将等于n，所以当你回到外循环的顶部时，检查$ i
也许你应该做的是：
for(i=0;i<n;i++)
{
String s=bf.readLine();
String user="",score="";
user=s.substring(0,s.indexOf(","));
s=s.substring(s.indexOf(",")+1);
score=s;
myplayer[i]=new Player(user,Double.parseDouble(score));
mynewplayer[i]= new Player(user,Double.parseDouble(score));
}
mynewplayer[x]=new Player(<the new username>,Double.parseDouble(<the new score>));