表达式错误的非法开始：两行错误？
问题描述：
我正在学习作为初学者的学校编码项目。我写的代码很混乱，不太好看，但这是我如何理解它的写法。我只剩下三条线上的18个错误，无法确定我出错的地方。这里是我的错误：表达式错误的非法开始：两行错误？
Band.java:42: illegal start of expression
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: illegal start of expression
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: ';' expected
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: '.class' expected
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: ';' expected
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: <identifier> expected
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: illegal start of expression
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: ';' expected
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: not a statement
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: ';' expected
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:42: ';' expected
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
^
Band.java:85: 'else' without 'if'
} else {
^
Band.java:115: illegal start of expression
private static double totalWeight(double []singleRow){
^
Band.java:115: illegal start of expression
private static double totalWeight(double []singleRow){
^
Band.java:115: ';' expected
private static double totalWeight(double []singleRow){
^
Band.java:115: '.class' expected
private static double totalWeight(double []singleRow){
^
Band.java:115: ';' expected
private static double totalWeight(double []singleRow){
^
Band.java:123: reached end of file while parsing
}
^
18 errors
这里是我的代码：
import java.util.Scanner;
//=============================================================================
public class Band {
//-----------------------------------------------------------------------------
private static Scanner keyboard = new Scanner(System.in);
//-----------------------------------------------------------------------------
public static void main(String[] args) {
int numberRows;
double [][] positions;
double total;
int numberPositions;
System.out.println("Welcome to Band of the Hour");
System.out.println("Please enter number of rows: ");
numberRows = keyboard.nextInt();
while (numberRows < 0 && numberRows > 10) {
System.out.println("Out of range, try again: ");
numberRows = keyboard.nextInt();
}
positions = new int[numberRows][];
for (int index=0; index<numberRows; index++) {
System.out.println("Please enter number of positions in row " + (char)(rowNumber + (int)'A') + " : ");
numberPositions = keyboard.nextInt();
while (numberPositions < 1 && numberPositions > 8) {
System.out.println("Out of range, try again: ");
}
positions = new double[numberRows][numberPositions];
}
for(int i=0; i < positions.length; i++) {
for(int j=0; j< positions[i].length; j++) {
positions[i][j] = 0.0;
}
calculate(numberRows, positions, rowNumber, total);
}
//-----------------------------------------------------------------------------
private static void calculate (int numberRows, double[][] positions, int[] rowNumber, double total) {
char operation;
int rowLetter;
int positionNumber;
double weight;
do {
System.out.println("(A)dd, (R)emove, (P)rint, e(X)it : ");
operation = keyboard.next().toUpper().charAt(0);
switch (operation) {
case 'A':
System.out.println("Please enter row letter :");
rowLetter = (int)keyboard.next().toUpper().charAt(0)-'A';
if (rowLetter < numberRows) {
System.out.println("Please enter position number (1 to" + positions[rowNumber].length + ") :");
positionNumber = keyboard.nextInt();
if (positionNumber >= 1 && positionNumber <= positions[rowNumber].length) {
System.out.println("Please enter weight (45.0 to 200.0)");
weight = keyboard.nextDouble();
if (weight >= 45.0 && weight <= 200.0) {
if (total <= 100 * positions[rowNumber].length) {
if (0 = positions[rowNumber][positionNumber]) {
weight = positions[rowNumber][positionNumber];
System.out.println("****** Musician added.");
} else {
System.out.println("There is already a musician there. :");
}
} else {
System.out.println("That would exceed the row weight limit :");
}
} else {
System.out.println("ERROR: Out of range, try again :");
}
} else {
System.out.println("Out of range, try again");
weight = keyboard.nextDouble();
if (weight >= 45.0 && weight <= 200) {
weight = positions[rowNumber][positionNumber];
} else {
System.out.println("Out of range, try again");
weight = keyboard.nextDouble();} else {
System.out.println("Out of range, try again :");
positionNumber = keyboard.nextInt();
}
}
break;
case 'R':
System.out.println("Please enter row letter :");
rowLetter = (int)keyboard.next().toUpper().charAt(0)-'A';
if (rowLetter < numberRows) {
System.out.println("Please enter position number (1 to" + positions[rowNumber].length + ") :");
positionNumber = keyboard.nextInt();
if (positions[rowNumber][positionNumber] =! 0) {
positions[rowNumber][positionNumber] = 0;
System.out.println("****** Musician removed.");
} else {
System.out.println("That position is vacant :");
}
} else {
System.out.println("Out of range, try again :");
}
break;
case 'P':
System.out.printf("%5d ", positions[rowNumber][positionNumber]);
break;
default: System.out.println("Out of range, try again");
}
} while (operation != 'X');
}
//-----------------------------------------------------------------------------
private static double totalWeight(double []singleRow){
int index;
double total = 0.0;
for(index = 0; index < singleRow.length; index++){
total = total + singleRow[index];
}
return total;
}
}
//=============================================================================
答
第85行的错误是不言而喻的：“其他没有如果”。 85号线是线82的else块起始的右括号与此else块的问题是，它不遵循if语句块：
if (weight >= 45.0 && weight <= 200) { // this line's got your if...
weight = positions[rowNumber][positionNumber];
} else { // this is fine
System.out.println("Out of range, try again");
weight = keyboard.nextDouble();
} else { // this is causing the problem
System.out.println("Out of range, try again :");
positionNumber = keyboard.nextInt();
} // this line is where the compiler is returning the error
// it's the end of the problematic else block
“达到文件结束，而解析”的错误方式你可能在你的代码末尾丢失了一个右括号（这个东西：}）。使用一致的缩进模式通常是一个好主意。这样可以更容易地发现哪些开启和关闭支撑相互匹配，并且更容易查看哪些线路位于哪些环路和语句块的内部或外部。使用IDE也是一个好主意;它可以帮助您不仅适当地格式化，还可以显示哪些大括号与哪些大括号相匹配（例如，如果您单击Netbeans中的一个大括号，它会突出显示大括号及其匹配的一个为黄色;如果它没有匹配一个，它以红色突出显示，因此您可以轻松判断您是否有太多或太少的右花括号）。
我不确定是什么原因导致“非法表达式”错误，但很可能您可能错过了主要方法或之前不同方法中的右大括号。 “非法启动表达式”错误的一个原因是编译器在另一个方法中看到一个方法头。你的方法头文件看起来很好，所以如果在解决“表达式非法启动”错误时它会给你的这些行上的其他错误将得到解决，那么我不会感到惊讶 - 一个错字有时会导致编译器返回几个错误在遇到问题的代码段中。
你需要学习如何让你的IDE格式化你的源代码。所有流行的IDE都可以为你做到这一点。然后，更容易看出问题所在，因为大括号会正确缩进。 –
你的代码如此令人难以置信地充满了错误，无法找到从哪里开始。你使用不存在的变量来分配双精度，调用不退出的方法，不闭合花括号，使用int []作为int，尝试赋值给常量等等。我建议你先从小程序，让它免于错误，然后转向更大的东西。 –