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[英]reading/writing a set to a .ser file compared to a .txt file in java
[英]Reading and Writing to a .txt file in Java
这是我分配作业的提示:您的程序需要从文本文件读取信息,而不是使用扫描仪从命令行读取信息。 您的程序还需要将消息写到文本文件中,而不是在屏幕上显示消息。
我已编写并运行代码以使用CLI进行提示。 但是,我绝对不知道如何利用文本文件更改代码。 有人可以向我解释一下吗?
到目前为止的代码:
import java.util.*;
public class parallelArrays {
public static void main(String[] args) {
String[] names;
int[] exam1Grades;
int[] exam2Grades;
int n, sum1, sum2;
double avg1,avg2;
Scanner kb = new Scanner(System.in);
// Get the number of students from the user
System.out.print("Enter # of students:");
n = kb.nextInt();
// Allocate the arrays
names = new String[n];
exam1Grades = new int[n];
exam2Grades = new int[n];
// Input the names and grades
for (int i=0; i<=names.length-1; i++) {
System.out.print("Enter name for student #" + (i+1) + ":");
names[i] = kb.next();
System.out.print("Enter exam #1 grade:");
exam1Grades[i] = kb.nextInt();
System.out.print("Enter exam #2 grade:");
exam2Grades[i] = kb.nextInt();
}
// Add up all the grades (could have been done in the above loop)
sum1 = 0;
sum2 = 0;
for (int i=0; i<=names.length-1; i++) {
sum1 = sum1 + exam1Grades[i];
sum2 = sum2 + exam2Grades[i];
}
// Calculate and output the averages
avg1 = sum1/n;
System.out.println();
System.out.println("Exam #1 average: " + avg1);
avg2 = sum2/n;
System.out.println("Exam #2 average: " + avg2);
System.out.println();
// Compare each grade to the average
for (int i=0; i<=names.length-1; i++) {
if (exam1Grades[i] > avg1)
System.out.println("Student " + names[i] + " is above average on exam 1");
else if (exam1Grades[i] < avg1)
System.out.println("Student " + names[i] + " is below average on exam 1");
else
System.out.println("Student " + names[i] + " is average on exam 1");
if (exam2Grades[i] > avg2)
System.out.println("Student " + names[i] + " is above average on exam 2");
else if (exam2Grades[i] < avg2)
System.out.println("Student " + names[i] + " is below average on exam 2");
else
System.out.println("Student " + names[i] + " is average on exam 2");
}
}
}
就像@Shobit前面说过的,将BufferedWriter与FileWriter结合使用,并通过write()和newLine()方法可以将所需的行插入文件中,而不是使用Println。
BufferedWriter writer = new BufferedWriter(new FileWriter("path-of-file")); //you don't need to create a File object, FileWriter takes a string for the filepath as well
writer.write("Student number...");
writer.writeLine(); //for a new line in the file
当您完成写入文件后,
writer.close();
您可以使用BufferedReader和BufferedWriter在Java中读取/写入文件。 BufferedReader构造函数采用FileReader对象,而其构造函数采用File对象。 看起来像这样:
BufferedReader br = new BufferedReader(new FileReader(new File("path-of-file")));
然后,您可以使用BufferedReader的readLine()
(或任何其他方法,具体取决于您的用例)从文件逐行读取。
以此类推,还有BufferedWriter和FileWriter以及用于write()
方法。
读/写后关闭读者流和作家流总是一个好习惯。 您可以在流上使用close
方法执行相同的操作。
希望能有所帮助。
import java.nio.file.path;
import java.nio.file.paths;
class FileCopy {
public static void main(String args[])
{
Path sour =Paths.get("Source path");
Path dest =Paths.get("destination path"); // The new file name should be given
or else FileAlreadyExistsException occurs.
Files.copy(sour, dest);
}
}
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