Question

我正在创建一些项目，用于将小数转换为二进制和返回。我明白了：此行有多个标记

Syntax error on token ";", Identifier expected
Syntax error on token ".", @ expected after

涉及我的第一个System.out.println()方法。为什么这不能编译？

package numbers;

import java.util.Scanner;

class DecimalBinaryWork {
    DecimalBinaryWork() {
    }
    String number = "-1";       
    Scanner scan = new Scanner(System.in);
    System.out.println("Enter in type: binary is 0 or decimal which is 10\n");
    number = scan.next();
    if (number != "0" && number != "10") {
        System.out.println("Error: Enter in 0 for binary or 10 for decimal. Try again");
        number = scan.next();
    }
    else if (number == "-1") {
        System.out.println("Enter in some type please");
    }
    else {
        convert(number);
    }

    String convert(String aString) {
        //fill in later
    }
}

Answer 1

您的代码不在函数中。看起来你试图创建一个构造函数，但没有将代码分成单独的函数

尝试：

class DecimalBinaryWork {
    public DecimalBinaryWork() {
    }

    public static void main(String[] args) {
        String number = "-1";
        Scanner scan = new Scanner(System.in);
        System.out.println("Enter in type: binary is 0 or decimal which is 10\n");
        number = scan.next();
        if (number != "0" && number != "10") {
            System.out.println("Error: Enter in 0 for binary or 10 for decimal. Try again");
            number = scan.next();
        }
        else if (number == "-1") {
            System.out.println("Enter in some type please");
        }
        else {
            // convert(number);
        }
    }

    public String convert(String aString) {
        return null;
        // fill in later
    }
}

Answer 2

你可能想在main方法中编写逻辑。

package com.test;

import java.util.Scanner;

class DecimalBinaryWork {
DecimalBinaryWork() {
}

private static String number = "-1";

public static void main(String[] str) {
    Scanner scan = new Scanner(System.in);
    System.out.println("Enter in type: binary is 0 or decimal which is 10\n");
    number = scan.next();
    if (number != "0" && number != "10") {
        System.out.println("Error: Enter in 0 for binary or 10 for decimal. Try again");
        number = scan.next();
    } else if (number == "-1") {
        System.out.println("Enter in some type please");
    } else {
        convert(number);
    }
}

private static String convert(String aString) {
    // fill in later
}

}

Answer 3

我会为你的班级创建一个独立的功能来完成你的逻辑。您可以将逻辑放入main中，也可以为该对象创建一个方法，为您的逻辑调用方法，如下所示：

public void DetermineDecimalBinaryWork() 
{
    String number = "";     
    Scanner scan = new Scanner(System.in);
    //ask for input until you get a valid response
    do {
        System.out.println("Enter in type: binary is 0 or decimal which is 10\n");
        number = scan.nextLine();
        if(!number.equals("0") && !number.equals("10"))
            System.out.println("Error: Invalid Input! Try again");

    } while (!number.equals("0") && !number.equals("10"));

    if (number.equals("-1")) {
        System.out.println("Enter in some type please");
    }
    else {
        convert(number);
    }

}

如何将函数与对象一起使用的示例

 public static void main(String[] args) {
     DecimalBinaryWork worker = new DecimalBinaryWork();
     worker.DetermineDecimalBinaryWork();
 }

Answer 4

您的System.out.println来电不在方法中。在方法之外但在类体内部，您可以做的只是声明字段和方法，并且方法之外的前一行位置被解释为声明并初始化名为scan的字段。 println语句既不是赋值也不是声明，因此它是语法错误。将代码放入方法中，例如main。

代码中缺少有效标记

4 个答案: