Question

我的java程序只将一行写入txt文件。

代码：主要：

package hu.hymosi.tut;

import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Random;

public class Main {

public static void main(String[] args) {
    PrintWriter out = null;
    frameworkcucc fw = new frameworkcucc();
    for (int i = 1; i < 100; i++) {
        Random rand = new Random();
        System.out.println(i);

        try {
            out = new PrintWriter("valtozok.txt");
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        int kiirando = rand.nextInt();

        fw.writetotext(kiirando, out);
    }
}

}

frameworkcucc：

package hu.hymosi.tut;

import java.io.PrintWriter;

public class frameworkcucc {

public void writetotext(int write, PrintWriter writer) {
    writer.print(write + "\n");
}

}

如果我运行该程序，它只会在我的txt文件中写入一行。什么是错误，我该如何解决？

Answer 1

您正在每次迭代中创建一个新的PrintWriter。把它移到循环外面。

try {
            out = new PrintWriter("valtozok.txt");
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

 for (int i = 1; i < 100; i++) {
        Random rand = new Random();
        System.out.println(i);
        int kiirando = rand.nextInt();

        fw.writetotext(kiirando, out);
    }
}

清理资源也是一种很好的做法，它也会刷新缓冲区：

out.close()

Answer 2

您需要flush PrintWriter Random才能将文字添加到您的文件中。

其他观察：

仅在循环外

PrintWriter

仅在循环外部初始化package test; import java.io.FileNotFoundException; import java.io.PrintWriter; import java.util.Random; public class Main { public static void main(String[] args) { // initialized before loop PrintWriter out = null; // proper naming convention Frameworkcucc fw = new Frameworkcucc(); try { out = new PrintWriter("valtozok.txt"); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } // initialized before loop Random rand = new Random(); for (int i = 1; i < 100; i++) { System.out.println(i); int kiirando = rand.nextInt(); fw.writetotext(kiirando, out); } // flushing and closing out.flush(); out.close(); } } class Frameworkcucc { public void writetotext(int write, PrintWriter writer) { writer.print(write + "\n"); } }一次，并在循环之前检查空值

这是一些略微改进的代码（请注意包等已更改）。

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Java printwriter只写一行

2 个答案: