我遇到从命令提示符运行java程序的问题。我有一个名为DataRecover的java文件，我有一个名为Triple的第二个java文件。现在，当我在命令提示符下运行javac Triple.java时，它会执行它应该执行的操作。但是，当我运行javac DataRecover.java时，它会出现以下错误消息：“线程中的异常”主“java.lang.NoClassDefFoundError：DataRecover（错误的名称：projectbeng \ DataRecover
编辑：我已经包括了这两个课程。我现在能够运行javac命令，并且在适当的文件夹中有每个CLASS文件。现在，我需要在命令提示符下运行DataRecover文件。当我运行“java DataRecover”时，我收到以下错误：“线程中的异常”主“java.lang.NoClassDefFoundError：DataRecover（错误名称：projectbeng \ DataRecover）”。DataRecover.java:61：错误：找不到符号
static Triple extractTriples（String str）{
^
符号：class Triple
location：class DataRecover
DataRecover.java:30：错误：找不到符号
三重三元组= extractTriples（线）;
^
符号：class Triple
location：class DataRecover
package projectbeng;
import java.util.Scanner;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.File;
import java.io.IOException;
public class DataRecover {
public static void main(String[] args) throws Exception {
//Create a Scanner for the user
Scanner sc = new Scanner(System.in);
System.out.print("Enter file name to process: ");
File fileName = new File(sc.nextLine() + ".txt"); //Do not include the .txt extension
if(!fileName.exists()){ //does not exist
throw new IOException("File \"" + fileName + "\" not found.");
}
System.out.println("\nProcessing file: " + fileName + "\n----------------------------------------");
BufferedReader br = new BufferedReader(new FileReader(fileName));
int lineCount = 0; //assumes file does not end with a new line character
int tripleLineCount = 0;
int tripleCount = 0;
String line = "";
//Read data from file
while((line = br.readLine()) != null){ //has another line in the file
lineCount++;
if(!line.equals("")) { //is not a blank line
Triple triples = extractTriples(line);
if(triples.getHasTriple()) { //line contains triples
System.out.println(triples.getTriples());
tripleLineCount++;
}
for(int j = 0; j < triples.getTriples().length(); j++) {
if(triples.getTriples().charAt(j) == '(') tripleCount++;
}
}
}
//prints out the summary of the file
System.out.println("\nSummary\n----------------------------------------");
System.out.println("Total lines: " + lineCount);
System.out.println("Lines containing triples: " + tripleLineCount);
System.out.println("Total number of triples: " + tripleCount);
}
/*Given a string, returns a Triple with a string containing the triples (if any) and a boolean stating whether
or not it contains a triple.
Assumptions:
1.) If a '-' sign is found, it has been added. If preceeding a number (for example -32), the number is 32 where
the '-' sign is simply garbage.
2.) If a '.' is found in a number (for example 2.32), the potential integers are 2 and 32 where the '.' is
garbage.
3.) For part c, if the first valid character found is a letter, this will always be the real triple. It does not
matter whether or not it is part of a word (for example, if it comes across "Dog a", 'D' will be the triple.)
4.) The strings "<null>", "<cr>", "<lf>", and "<eof>" as well as multi-digit numbers (ex. 32) count as single
characters. Thus, they cannot be broken up (no garbage in between the characters).
*/
static Triple extractTriples(String str) {
/*Grammar:
Triple is in form (a,b,c) where a is either a non-negative integer or the string "<null>", b is a
non-negative integer where b <= a (b must be 0 if a is <null>), and c is either an individual letter
(upper or lower case), period, colon, semicolon, or one of the three strings "<cr>", "<lf>", or "<eof>".
state == 0 ==> needs left parenthesis
state == 1 ==> needs right parenthesis
state == 2 ==> needs comma
state == 3 ==> needs a
state == 4 ==> needs b
state == 5 ==> needs c
*/
int state = 0;
int a = -1;
int b = -1;
String triples = "";
String tempTriples = "";
for(int i = 0; i < str.length(); i++) {
if(str.charAt(i) == '.' || str.charAt(i) == ':' || str.charAt(i) == ';' || str.charAt(i) == '<' ||
(str.charAt(i) >= 'a' && str.charAt(i) <= 'z') || (str.charAt(i) >= 'A' && str.charAt(i) <= 'Z')
|| (str.charAt(i) >= '0' && str.charAt(i) <= '9') || str.charAt(i) == ',' ||
str.charAt(i) == '(' || str.charAt(i) == ')') {
if(state == 0) {
if(str.charAt(i) == '(') {
tempTriples = str.substring(i, i+1);
state = 3;
}
}else if(state == 1) {
if(str.charAt(i) == ')') {
triples = triples + tempTriples + str.substring(i, i+1) + " ";
tempTriples = "";
state = 0;
a = -1;
b = -1;
}
}else if(state == 2) {
if(str.charAt(i) == ',') {
tempTriples = tempTriples + str.substring(i, i+1);
if(b != -1) state = 5;
else state = 4;
}
}else if(state == 3) {
if(str.charAt(i) >= '0' && str.charAt(i) <= '9') {
int j = i;
while(j < str.length() && str.charAt(j) >= '0' && str.charAt(j) <= '9') j++;
a = Integer.parseInt(str.substring(i, j));
i = j - 1;
tempTriples = tempTriples + a;
state = 2;
}else if(str.length() > i + 5 && str.substring(i, i+6).equals("<null>")) {
a = 0;
tempTriples = tempTriples + str.substring(i, str.indexOf(">", i)+1);
i = str.indexOf(">", i);
state = 2;
}
}else if(state == 4) {
if(str.charAt(i) >= '0' && str.charAt(i) <= '9') {
int j = i;
while(j < str.length() && str.charAt(j) >= '0' && str.charAt(j) <= '9') j++;
b = Integer.parseInt(str.substring(i, j));
i = j - 1;
if(b <= a) {
tempTriples = tempTriples + b;
state = 2;
}else b = -1;
}
}else if(state == 5) {
if(str.charAt(i) == '.' || str.charAt(i) == ':'||(str.charAt(i) <= 'z' && str.charAt(i) >= 'a')
|| str.charAt(i) == ';' || (str.charAt(i) <= 'Z' && str.charAt(i) >= 'A')) {
tempTriples = tempTriples + str.substring(i, i+1);
state = 1;
}else if((str.length() > i + 4 && str.substring(i, i+5).equals("<eof>")) ||
(str.length() > i + 3 && (str.substring(i, i+4).equals("<cr>") ||
str.substring(i, i+4).equals("<lf>")))) {
tempTriples = tempTriples + str.substring(i, str.indexOf(">", i)+1);
i = str.indexOf(">", i);
state = 1;
}else if(str.length() > i + 5 && str.substring(i, i+6).equals("<null>")) {
i = str.indexOf(">", i);
}
}
}
}
Triple triple = new Triple(true, triples);
if(triples.equals("")) triple.setHasTriple(false); //does not contain a triple
return triple;
}
package projectbeng;
class Triple {
boolean hasTriple = this.hasTriple;
String triple = this.triple;
//creates a new Triple
Triple(boolean newHasTriple, String newTriple){
this.hasTriple = newHasTriple;
this.triple = newTriple;
}
//returns whether or not Triple contains any triples
boolean getHasTriple() {
return hasTriple;
}
//returns the triples in Triple
String getTriples() {
return triple;
}
//changes the state of whether a Triple contains triples
void setHasTriple(boolean newHasTriple){
this.hasTriple = newHasTriple;
}
}
通过命令提示符运行DataRecover文件的正确方法是什么？
答案 0 :(得分：1)
当您在其他文件中引用源文件时，您必须将所有这些文件放在一起。在你的情况下应该是：
javac Triple.java DataRecover.java
许多现代Java项目使用构建工具来帮助管理源文件。两个流行的Java构建工具是Gradle和Maven。