I am a total newbie in Java and Eclipse. I googled for lots of help but still confused. From Eclipse I click run then choose Java application and I get this error immediately. Here is my source code:
import java.util.Arrays;
import java.util.Scanner;
public class SliceandDice {
void main(String args[]) {
System.out.println("This is the BIGGEST program console");
System.out.println("Each input line will be a pair of numbers separated by a COMMA.");
System.out.println("First number must be an unsigned number less than 10000. Max example: 9999");
System.out.println("Second number is the 'target' number.");
System.out.println("Example of an input line to be typed:");
System.out.println(" 4721 , 75");
for (int i = 1; i < 6; i++) // each time in this loop, we have a new
// set.
{
System.out.println("Type a pair of numbers according to the syntax rules above:");
String iLine; // Declare a variable to hold the name.
Scanner in = new Scanner(System.in);
iLine = in.nextLine(); // Read one line from the console.
in.close(); // Note 2
NumberSet set = ParseRawInput(i, iLine);
if (set.IsValid()) {
System.out.println("Valid inputs. Card Number to tear apart:" + set.getCardNumber()
+ "; Target Number: " + set.getTargetNumber());
String cardNumber = set.getCardNumber();
int target = set.getTargetNumber();
AnalyzeNumber(cardNumber, target); // solve for this set of
// numbers
} else {
System.out.println("Invalid set of numbers. Enter in format: nnnn,tttt");
}
}
}
private void AnalyzeNumber(String cn, int t) {
int n = cn.length();
int m = n;
int sums = 4 + 3 + 2 + 1;
int[] possibleAnswers = new int[sums];
int answer = 0;
for (int digits = 1; digits < m; digits++) {
possibleAnswers[answer] = PossibleAnswer(0, digits, cn);
answer++;
}
System.out.println("-----------");
possibleAnswers[answer] = PossibleAnswer(1, 2, cn);
answer++;
possibleAnswers[answer] = PossibleAnswer(1, 3, cn);
answer++;
System.out.println("-----------");
possibleAnswers[answer] = PossibleAnswer(2, 2, cn);
answer++;
System.out.println("-----------");
int finalAnswer = FindBiggestNearTarget(possibleAnswers, t);
System.out.println("Best sum (closet to target) = " + String.valueOf(finalAnswer));
}
private int PossibleAnswer(int extender, int lengthDigits, String cn) {
// extender => which digit position gets multilength adjustment
int n = cn.length();
int[] number = new int[n]; // holds individual addends
int sum = 0;
int LEN = 1; // default length when we need it
String addends = "";
int i;
if (extender == 0) {
i = 0;
while (i < n) {
addends += cn.substring(i, lengthDigits) + " + ";
number[i] = Integer.parseInt(cn.substring(i, lengthDigits));
sum += number[i];
i = i + lengthDigits; // always increment at least 1 position
if (i + lengthDigits > n)
lengthDigits = 1;
}
System.out.println(addends + " = " + String.valueOf(sum));
return sum;
}
if (extender == 1) {
i = 0;
while (i < n) {
addends += cn.substring(i, LEN) + " + ";
number[i] = Integer.parseInt(cn.substring(i, LEN));
sum += number[i];
if (i == 0) {
i++;
LEN = lengthDigits;
} else if (i == 1) {
i = i + lengthDigits; // i = 3 (last number)
LEN = 1;
} else if (i == 2) {
i = 1;
LEN = 3;
} else {
i = n; // force exit of while loop
}
if (i + LEN > n)
LEN = 1;
}
System.out.println(addends + " = " + String.valueOf(sum));
return sum;
}
if (extender == 2) {
i = 0;
while (i < n) {
addends += cn.substring(i, LEN) + " + ";
number[i] = Integer.parseInt(cn.substring(i, LEN));
sum += number[i];
i = i + LEN; // always increment at least 1 position
if (i == extender) {
LEN = lengthDigits;
}
if (i + LEN > n)
i = n; // force out of loop
}
System.out.println(addends + " = " + String.valueOf(sum));
return sum;
}
return 0;
}
private int FindBiggestNearTarget(int[] possibles, int target) {
int[] sumArray = possibles;
Arrays.sort(sumArray);
// temporary variable for swapping values
int temp;
// reverse the array
for (int i = 0; i < sumArray.length / 2; ++i) {
temp = sumArray[i];
sumArray[i] = sumArray[sumArray.length - i - 1];
sumArray[sumArray.length - i - 1] = temp;
}
for (int i = 0; i < sumArray.length; i++) {
if (sumArray[i] < target) {
return sumArray[i];
}
}
return -1; // should not occur
}
public static NumberSet ParseRawInput(int i, String rawInput) {
NumberSet errorSet = new NumberSet(-1, "", 0);
// string[] stringArray = rawInput.Split( new char[] { ','});
String[] stringArray = rawInput.toString().split(rawInput, ',');
if (stringArray.length != 2)
return errorSet; // ensure 2 tokens separated by comma
// work on 1st token:
String cardNumberString = stringArray[0].trim(); // trim any whitespace
// from this token
if (cardNumberString.length() > 4)
return errorSet; // ensure token is 4 bytes or less
// declare token as integer
int cardNumber = Integer.parseInt(cardNumberString);
// work on 2nd token:
String targetNumberString = stringArray[1].trim(); // trim any
// whitespace from
// token
if (targetNumberString.length() > 4)
return errorSet; // ensure token is 4 bytes or less
int targetNumber = Integer.parseInt(targetNumberString); // convert into
// int
NumberSet validSet = new NumberSet(i, cardNumberString, targetNumber);
return validSet;
}
}
class NumberSet {
// Java getter & setter
private String CardNumber;
private int TargetNumber;
private int SetNumber;
public int getSetNumber() {
return this.SetNumber;
}
public String getCardNumber() {
return this.CardNumber;
}
public int getTargetNumber() {
return this.TargetNumber;
}
public NumberSet(int sn, String cn, int t) {
this.SetNumber = sn;
this.CardNumber = cn;
this.TargetNumber = t;
}
public Boolean IsValid() {
if (this.SetNumber < 0)
return false;
return true;
}
}
Mudassir
You cannot define the main method as you do in C++.
For the Java interpreter, the main method must always be public and static. So you need to change your main method signature to
public static void main(String args[])
Try this, and feel free to ask further. :-)
Create a new project and make the build path to point to the existing source folders. This will resolve the "Selection does not contain a main type" error.
I also experienced this problem and could solve it. The solution was not mentioned yet.
In my case I'm working in Eclipse with Xtend and I converted the project to maven. After that there was a source-exclusion entry in your classpath file:
<classpathentry excluding="**" kind="src" output="target/classes" path="xtend-gen">
Then you just need to delete this line and do a clean build.
来源：https://stackoverflow.com/questions/4252472/java-launch-error-selection-does-not-contain-a-main-type