我在循環時遇到問題，我的錯誤涉及&&

Question

我的指導是編寫一個代碼（用Java），該代碼查找介於1,000到9,999（任意4位數字）之間的代碼，並符合以下四個條件：

1. 所有四個數字都不相同。
2. 千位數字是十位數的3倍。
3. 這個數字是奇數。
4. 這些數字的總和是27。

到目前為止，這就是我所擁有的。 我在//loop部分下遇到錯誤：

C4PP10.java:27: error: bad operand types for binary operator '&&'"

是出現的錯誤。

在我的腦海中， &&只是表示“和”，我是否使用不當？

這是我對Java類作業BTW的介紹。

public class C4PP10
{
    public static void main(String[] args)
    {
        //variables
        int first=1;
        int second=0;
        int third=0;
        int fourth=0;
        int total = first * 1000 + second * 100 + third * 10 + fourth;
        boolean fourDifferentDigits = false;
        boolean thousandsPlaceX3TensPlace = false;
        boolean odd = false;
        boolean sum = false;
        boolean correctAddress = false;

        //loop
        while (correctAddress = false)
        {
            fourth = fourth + 1;
            if (fourth == 10)
            {
                fourth = 0 && third = third + 1;
            }//end if
            if (third == 10)
            {
                third = 0 && second = second + 1;
            }//end if
            if (second == 10)
            {
                second = 0 && first = first + 1;
                total = first * 1000 + second * 100 + third * 10 + fourth;
            }//end if
        }//end loop


        //testing
        if ( first != second && first !=third && first !=fourth && second !=third &&                 second !=fourth && third != fourth )
        {
            fourDifferentDigits = true;
        }//end if

        if (first == third*3)
        {
            thousandsPlaceX3TensPlace = true;
        }//end if 

        if (fourth%2 != 0)
        {
            odd = true;
        }//end if

        if ( first + second + third + fourth == 27 )
        {
            sum = true;
        }//end if

        if (fourDifferentDigits=true && thousandsPlaceX3TensPlace=true && odd=true   && sum=true)
        {
            correctAddress = true;
        }//end if

        if (correctAddress = true)
        {
            System.out.println("The Riddler plans to strike " + total + " Pennsylvania     Avenue!");
        }

    }//end main
}//end class

Answer 1

這么多格式錯誤，請確保比較時使用==而不是=來表示布爾語句，並確保使用縮進以提高可讀性。 僅在邏輯語句中使用&& ，而不是在語句中添加。 您還可以在開始時使用逗號（ , ）定義多個變量，而不必每次都鍵入int 。

public class C4PP10
{
    public static void main(String[] args)
    {
        //variables
        int first = 1, second = 0, third = 0, fourth = 0;
        int total = first * 1000 + second * 100 + third * 10 + fourth;
        boolean fourDifferentDigits = false, thousandsPlaceX3TensPlace = false;
        boolean odd = false, sum = false, correctAddress = false;

        while (correctAddress == false) // or while (!(correctAddress))
        {
            fourth = fourth + 1;
            if (fourth == 10)
            {
                fourth = 0;
                third = third + 1;
            }                
            if (third == 10)
            {
                third = 0
                second = second + 1;
            }
            if (second == 10)
            {
                second = 0 
                first = first + 1;
                total = first * 1000 + second * 100 + third * 10 + fourth;
            }
        }


        if (first != second && first != third && first != fourth && second !=third && second !=fourth && third != fourth)
        {
            fourDifferentDigits = true;
        }

        if (first == third * 3)
        {
            thousandsPlaceX3TensPlace = true;
        }

        if (fourth % 2 != 0)
        {
            odd = true;
        }

        if (first + second + third + fourth == 27)
        {
            sum = true;
        }

        if (fourDifferentDigits == true && thousandsPlaceX3TensPlace == true && odd == true && sum == true)
        {
            correctAddress = true;
        }

        if (correctAddress == true)
        {
            System.out.println("The Riddler plans to strike " + total + " Pennsylvania Avenue!");
        }

    }
}