java - 打印出在字符串中找到字符的行号

Question

我正在编写一个程序来扫描给定字符串中的数学运算符，当程序找到匹配项时，我想返回该运算符以及找到它的行，下面是我的尝试。

public class Testing {

    public enum TokenType {

        OP_MULTIPLY,
        OP_DIVIDE,
        OP_MOD,
        OP_ADD,
        OP_SUBTRACT,
        OP_LESS,
        OP_LESSEQUAL,
        OP_GREATER,
        OP_GREATEREQUAL,
        OP_EQUAL,
        OP_NOTEQUAL,
        OP_NOT,
        OP_ASSIGN,
        OP_AND,
        OP_OR,
        OP_DOT

    }

    public static String inputString = "public class HelloWorld {\n"
            + " public static void-*//-- main(String[] args) {\n" + " // to print out+8+*+ hello world\n"
            + " System.out.println(\"Hello World!\");\n" + " }\n" + "}\n";

    public static void lineNumber(String lineNumber) {
        int count = 1;

        String[] lines = inputString.split("\\r?\\n");
        for (String line : lines) {
            System.out.println("line " + count++);
        }

        int n = inputString.length();
        for (int i = 0; i < n; i++) {
            char ch = inputString.charAt(i);
            getOP(ch);

        }
    }

    public static TokenType getOP(char ch) {

        switch (ch) {
        case '+':
            System.out.println(TokenType.OP_ADD + ", " + ch);
            return TokenType.OP_ADD;

        case '-':
            System.out.println(TokenType.OP_SUBTRACT + ", " + ch);
            return TokenType.OP_SUBTRACT;

        case '/':
            System.out.println(TokenType.OP_DIVIDE + ", " + ch);
            return TokenType.OP_DIVIDE;

        case '*':
            System.out.println(TokenType.OP_MULTIPLY + ", " + ch);
            return TokenType.OP_MULTIPLY;
        }

        return null;

    }

    public static void main(String[] args) {
        lineNumber(inputString);
    }
}

这是我当前的输出:

line 1
line 2
line 3
line 4
line 5
line 6
OP_SUBTRACT, -
OP_MULTIPLY, *
OP_DIVIDE, /
OP_DIVIDE, /
OP_SUBTRACT, -
OP_SUBTRACT, -
OP_DIVIDE, /
OP_DIVIDE, /
OP_ADD, +
OP_ADD, +
OP_MULTIPLY, *
OP_ADD, +

我想要实现什么:

Line 1: OP_ADD, +
Line 3: OP_MULTIPLY, *
etc.

谢谢

Answer 1

您的代码可能如下所示:

public class Testing {

    enum TokenType {

        OP_MULTIPLY,
        OP_DIVIDE,
        OP_MOD,
        OP_ADD,
        OP_SUBTRACT,
        OP_LESS,
        OP_LESSEQUAL,
        OP_GREATER,
        OP_GREATEREQUAL,
        OP_EQUAL,
        OP_NOTEQUAL,
        OP_NOT,
        OP_ASSIGN,
        OP_AND,
        OP_OR,
        OP_DOT

    }

    public static void main(String[] args) {
        lineNumber();
    }

    public static final String inputString = "public class HelloWorld {\n" +
            " public static void-*//-- main(String[] args) {\n" +
            " // to print out+8+*+ hello world\n" +
            " System.out.println(\"Hello World!\");\n" +
            " }\n" +
            "}\n";

    private static void lineNumber() {
        String[] lines = inputString.split("\\r?\\n");
        for (int i = 0; i < lines.length; i++) {
            String line = lines[i];
            for (int j = 0; j < line.length(); j++) {
                TokenType tokenType = getOP(line.charAt(j));
                if (tokenType != null) {
                    System.out.printf("Line %d: %s, %s\n", i + 1, tokenType.name(), line.charAt(j));
                }
            }
        }
    }

    private static TokenType getOP(char ch) {
        switch (ch) {
            case '+':
                return TokenType.OP_ADD;
            case '-':
                return TokenType.OP_SUBTRACT;
            case '/':
                return TokenType.OP_DIVIDE;
            case '*':
                return TokenType.OP_MULTIPLY;
            // more
        }
        return null;
    }
}

嵌套循环允许保留当前行索引。此外，您的 getOP 方法应该只负责根据字符值确定数学运算。它不应该打印任何内容，这是 lineNumber 的责任。

输出:

Line 2: OP_SUBTRACT, -
Line 2: OP_MULTIPLY, *
Line 2: OP_DIVIDE, /
Line 2: OP_DIVIDE, /
Line 2: OP_SUBTRACT, -
Line 2: OP_SUBTRACT, -
Line 3: OP_DIVIDE, /
Line 3: OP_DIVIDE, /
Line 3: OP_ADD, +
Line 3: OP_ADD, +
Line 3: OP_MULTIPLY, *
Line 3: OP_ADD, +