打印出在 String 中找到 Char 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，我想返回运算符和找到它的行，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);
    }
}

这是我目前的 output：

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, +

我试图实现的目标：

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;
    }
}

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

Output：

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, +

Answer 2

您应该对每个单独的行进行操作检查，而不是一次对整个输入进行检查。

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

    String[] lines = inputString.split("\\r?\\n");
    for (String line : lines) {
        System.out.println("line " + count++);
        int n = line.length();
        for (int i = 0; i < n; i++)
        {
            char ch = line.charAt(i);
            getOP(ch);

        }
    }
}

Answer 3

所以关键是在与符号打印相同的循环中获取行号。 我还添加了一些复杂性以避免打印行号而没有任何内容。

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 = 0;

    String[] lines = inputString.split("\\r?\\n");
    for (String line: lines) {
        count++;
        int n = line.length();
        boolean first = true;
        for (int i = 0; i < n; i++) {
            char ch = line.charAt(i);
            if (getOP(ch, first, count) != null) {
                first = false;
            }

        }
        System.out.println();
    }


}



public static TokenType getOP(char ch, boolean firstOnLine, int lineNum) {
    if (firstOnLine && (ch == '+' || ch == '-' || ch == '/' || ch == '*')) {
        System.out.print("line " + lineNum + " ");
    }
    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);
}

}