HashCode循环不循环遍历字符串，程序不会因while循环而终止

时间：2013-10-05 03:48:57

标签： java for-loop while-loop hashcode

我需要我的程序遍历while循环并向用户询问无限数量的字符串......直到他们输入“Done”。如果他们内嵌的字符串不是“完成”，那么它会计算整个字符串的哈希码值并将其排序到正确的层中。一旦用户输入完成，程序将打印每层中的标签以及哪一层是最大的。

我的问题：程序要求用户输入一个字符串，计算每个字母的哈希值，将这些值排序到一个层中，打印标签，打印哪个等级最大。然后询问用户另一个字符串并继续此过程 - ＆gt; 程序永远不会终止。

FYI：我从while循环中取出了打印语句（在for循环之后），我得到一个编译错误：“找不到符号”指向我的所有“层”变量。我认为这意味着我需要声明它们在while循环的外部，但是如果我这样做，那么同样的问题就会发生，因为它们没有在内部声明 while循环。 / p>

我需要程序做什么：向用户询问字符串，计算哈希码，在适当的位置计算（进入适当的层）。继续此循环，直到用户输入“完成”，然后程序打印每层中的计算值，最后打印哪一层是最大的。

示例输出：

输入字符串：Foo
输入字符串：完成
大于或等于2,000,000,000：0
1,500,000,000至1,999,999,999：0
1,000,000,000至1,499,999,999：0
500,000,000至999,999,999：0
小于或等于499,999,999：1 最大存储桶小于或等于499,999,999，大小为1

**此外，我知道有一种更简单的方法来确定哪一层是最大的（第64-109行），但我无法弄清楚。我们没有在课堂上谈论过数组或类似内容，所以我不确定如何使用if / else语句来简化所有这些。** 

import java.util.Scanner;
public class StringHashCodeLoop {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
String strEntered;

// Prompt user for a string, store string in "strEntered."
System.out.println("Enter a String:");
strEntered = sc.next();

// Perform a while loop as long as the entered string does not equal "Done."
while (!strEntered.equals("Done")) {    
    // Convert all letters in the string to lower case.
    strEntered = strEntered.toLowerCase();

    // Declare the integer "length" and set it equal to the length of the entered string, to be used in the for loop.
    int length = strEntered.length();
    // Initialize each tier/bucket value to 0 before performing calculations.
    int tier1,tier2,tier3,tier4,tier5;
    tier1 = 0;
    tier2 = 0;
    tier3 = 0;
    tier4 = 0;
    tier5 = 0;

    for(int i = 0; i < length; ++i) {
        int hashValue = 0;
        hashValue += strEntered.charAt(i) * Math.pow(31, length - 1 - i);

        // Sort the Hash Code for the entered string into its corresponding bucket.
        if (hashValue >= 2000000000) {
            tier1++;
        }
        else if ((1500000000 < hashValue) && (hashValue < 1999999999)) {
            tier2++;
        }
        else if ((1000000000 < hashValue) && (hashValue < 1499999999)) {
            tier3++;
        }
        else if ((500000000 < hashValue) && (hashValue < 999999999)) {
            tier4++;
        }
        else {
            tier5++;
        }
    } // end of for loop

    System.out.println("Enter a String:");
    strEntered = sc.next();
} // end of while loop

// Print the tallied totals of each bucket.
System.out.println("Greater than 2,000,000,000: " + tier1);
System.out.println("1,500,000,000 to 1,999,999,999: " + tier2);
System.out.println("1,000,000,000 to 1,499,999,999: " + tier3);
System.out.println("500,000,000 to 999,999,999: " + tier4);
System.out.println("Less than or equal to 499,999,999: " + tier5);

// Print which is the largest bucket and the total of its contents.
    if (tier1 > tier2 && tier1 > tier3 && tier1 > tier4 && tier1 > tier5) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
    }
    else if (tier2 > tier1 && tier2 > tier3 && tier2 > tier4 && tier2 > tier5) {
        System.out.println("The largest bucket is 1,500,000,000 to 1,999,999,999 with a size of " + tier2);
    }
    else if (tier3 > tier1 && tier3 > tier2 && tier3 > tier4 && tier3 > tier5) {
        System.out.println("The largest bucket is 1,000,000,000 to 1,499,999,999 with a size of " + tier3);
    }
    else if (tier4 > tier1 && tier4 > tier2 && tier4 > tier3 && tier4 > tier5) {
        System.out.println("The largest bucket is 500,000,000 to 999,999,999 with a size of " + tier4);
    }
    else if (tier5 > tier1 && tier5 > tier2 && tier5 > tier3 && tier5 > tier4) {
        System.out.println("The largest bucket is Less than or equal to 499,999,999 with a size of " + tier5);
    }
    else if (tier1 == tier2) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
    }
    else if (tier1 == tier3) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
    }
    else if (tier1 == tier4) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
    }
    else if (tier1 == tier5) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
    }
    else if (tier2 == tier3) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier2);
    }
    else if (tier2 == tier4) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier2);
    }
    else if (tier2 == tier5) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier2);
    }
    else if (tier3 == tier4) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier3);
    }
    else if (tier3 == tier5) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier3);
    }
    else if (tier4 == tier5) {
        System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier4);
    }
}   
}

2 个答案:

答案 0 :(得分：0)

这应该做的工作：

import java.util.Scanner;
public class StringHashCodeLoop {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
String strEntered;

// Prompt user for a string, store string in "strEntered."
System.out.println("Enter a String:");
strEntered = sc.next();

// Perform a while loop as long as the entered string does not equal "Done."
while (!strEntered.equals("Done")) {    
    // Convert all letters in the string to lower case.
    strEntered = strEntered.toLowerCase();

    // Declare the integer "length" and set it equal to the length of the entered string, to be used in the for loop.
    int length = strEntered.length();
    // Initialize each tier/bucket value to 0 before performing calculations.
    int tier1,tier2,tier3,tier4,tier5;
    tier1 = 0;
    tier2 = 0;
    tier3 = 0;
    tier4 = 0;
    tier5 = 0;

    for(int i = 0; i < length; ++i) {
        int hashValue = 0;
        hashValue += strEntered.charAt(i) * Math.pow(31, length - 1 - i);

        // Sort the Hash Code for the entered string into its corresponding bucket.
        if (hashValue >= 2000000000) {
            tier1++;
        }
        else if ((1500000000 < hashValue) && (hashValue < 1999999999)) {
            tier2++;
        }
        else if ((1000000000 < hashValue) && (hashValue < 1499999999)) {
            tier3++;
        }
        else if ((500000000 < hashValue) && (hashValue < 999999999)) {
            tier4++;
        }
        else {
            tier5++;
        }
    } // end of for loop

    System.out.println("Enter a String:");
    System.out.println("Greater than 2,000,000,000: " + tier1);
    System.out.println("1,500,000,000 to 1,999,999,999: " + tier2);
    System.out.println("1,000,000,000 to 1,499,999,999: " + tier3);
    System.out.println("500,000,000 to 999,999,999: " + tier4);
    System.out.println("Less than or equal to 499,999,999: " + tier5);

    // Print which is the largest bucket and the total of its contents.
        if (tier1 > tier2 && tier1 > tier3 && tier1 > tier4 && tier1 > tier5) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
        }
        else if (tier2 > tier1 && tier2 > tier3 && tier2 > tier4 && tier2 > tier5) {
            System.out.println("The largest bucket is 1,500,000,000 to 1,999,999,999 with a size of " + tier2);
        }
        else if (tier3 > tier1 && tier3 > tier2 && tier3 > tier4 && tier3 > tier5) {
            System.out.println("The largest bucket is 1,000,000,000 to 1,499,999,999 with a size of " + tier3);
        }
        else if (tier4 > tier1 && tier4 > tier2 && tier4 > tier3 && tier4 > tier5) {
            System.out.println("The largest bucket is 500,000,000 to 999,999,999 with a size of " + tier4);
        }
        else if (tier5 > tier1 && tier5 > tier2 && tier5 > tier3 && tier5 > tier4) {
            System.out.println("The largest bucket is Less than or equal to 499,999,999 with a size of " + tier5);
        }
        else if (tier1 == tier2) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
        }
        else if (tier1 == tier3) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
        }
        else if (tier1 == tier4) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
        }
        else if (tier1 == tier5) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier1);
        }
        else if (tier2 == tier3) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier2);
        }
        else if (tier2 == tier4) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier2);
        }
        else if (tier2 == tier5) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier2);
        }
        else if (tier3 == tier4) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier3);
        }
        else if (tier3 == tier5) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier3);
        }
        else if (tier4 == tier5) {
            System.out.println("The largest bucket is Greater than 2,000,000,000 with a size of " + tier4);
        }

    strEntered = sc.next();
} // end of while loop

// Print the tallied totals of each bucket.
}   
}

如果您需要用户输入仅为Done，则使用equals方法本身。

关于移动线路： 你最初做的是使用strEntered = sc.next（）获得输入;在while循环之前。检查输入 - ＆gt;等于完成然后继续。

在while循环中： 扫描下一个输入后，它被转换为小写 - ＆gt;在下一次迭代中暗示，它不可能在前面用大写字母D“完成”。这就是我要求将扫描部分移动到while循环结束的原因

答案 1 :(得分：0)

移动线

int tier1,tier2,tier3,tier4,tier5;

在while循环之前，复制行

tier1 = 0;
…
tier5 = 0;

并在移动int tier1…行之后（仍然在while循环之上/之外）粘贴它。

这将消除编译器错误并让您的应用程序运行。

发生的事情是因为你在while语句和if语句中使用了层变量，你需要在包含两者的范围中声明变量。同时声明它们只意味着 while可以看到/使用它们。这就是你必须将代码移出的原因。

你必须复制那些初始化行（所有“tier＃= 0”行）的原因是因为变量肯定在if中使用if而不管while是否运行（例如，如果用户怎么办？将“完成”作为第一个输入）。但是，如果while循环永远不会运行，那么tier1等将全部未初始化，ifs将失败。

这就是为什么你必须给他们一些初始价值。在这种情况下零工作正常。

您只复制该代码（同时将其留在while中）的原因是因为您仍然需要将这些值重置为每个循环归零。

希望这是有道理和有帮助的。

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