[英]read a file using Scanner: Why am I getting an error when using Scanner for read files in java?
本示例演示了如何使用Scanner逐行读取文件(它不执行写操作)我不知道为什么在尝试编译时会出错。 有人可以向我解释原因吗? 我正在使用jcreatorLE和JDK 1.6运行我的程序:
import java.io.*;
import java.util.Scanner;
public final class File_read {
public static void main(String... aArgs) throws FileNotFoundException {
ReadWithScanner parser = new ReadWithScanner("C:\\Temp\\test.txt");
parser.processLineByLine();
log("Done.");
}
/**
* @param aFileName full name of an existing, readable file.
*/
public ReadWithScanner(String aFileName){
fFile = new File(aFileName);
}
/** Template method that calls {@link #processLine(String)}. */
public final void processLineByLine() throws FileNotFoundException {
Scanner scanner = new Scanner(fFile);
try {
//first use a Scanner to get each line
while ( scanner.hasNextLine() ){
processLine( scanner.nextLine() );
}
}
finally {
//ensure the underlying stream is always closed
scanner.close();
}
}
/**
* Overridable method for processing lines in different ways.
*
* <P>This simple default implementation expects simple name-value pairs, separated by an
* '=' sign. Examples of valid input :
* <tt>height = 167cm</tt>
* <tt>mass = 65kg</tt>
* <tt>disposition = "grumpy"</tt>
* <tt>this is the name = this is the value</tt>
*/
protected void processLine(String aLine){
//use a second Scanner to parse the content of each line
Scanner scanner = new Scanner(aLine);
scanner.useDelimiter("=");
if ( scanner.hasNext() ){
String name = scanner.next();
String value = scanner.next();
log("Name is : " + quote(name.trim()) + ", and Value is : " + quote(value.trim()) );
}
else {
log("Empty or invalid line. Unable to process.");
}
//(no need for finally here, since String is source)
scanner.close();
}
// PRIVATE //
private final File fFile;
private static void log(Object aObject){
System.out.println(String.valueOf(aObject));
}
private String quote(String aText){
String QUOTE = "'";
return QUOTE + aText + QUOTE;
}
}
这是运行它的结果:
--------------------Configuration: <Default>--------------------
C:\Users\administrador\Documents\File_read.java:15: invalid method declaration; return type required
public ReadWithScanner(String aFileName){
^
1 error
Process completed.
当您从此处提取代码时:-),您重命名了该类,但未重命名该构造函数。 只允许构造函数没有返回类型。
我建议您重命名该类或重命名该构造函数。
我希望这不是功课。 就目前而言,您的教育者将很容易证明time窃。 您至少需要更改变量名以及类名,您可能还需要对其进行一些重新格式化,包括更改类中方法的顺序。
那是功课。 不是吗? :-)
您的“ ReadWithScanner”构造函数需要匹配类的名称(“ File_read”)
public File_read(String aFileName){
fFile = new File(aFileName);
}
您的类名为File_read
,构造函数名为ReadWithScanner
。 警告是您的构造函数需要与该类相同的名称。
该类的名称为File_read,因此构造函数名称应为File_read,但您将名称命名为ReadWithScanner,这就是其抱怨的原因。 编译器认为它是方法名,因此期望返回类型。
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