java - Java 中的方法不返回任何内容

Question

我用 Java 编写了一个类，有 5 个方法。线性搜索，如果找到值则返回 true，如果未找到则返回 false。线性搜索 2，如果找到，则返回值的位置。二分查找。它也搜索数组中的值，打印 Int 数组，一次打印 10 个数字，以及选择排序，它对数组进行排序，以便我可以进行二分搜索。一切都编译正常，但由于某种原因，我的方法都没有返回任何内容(除了 void printIntArray 方法)。

编辑:

<小时/>

谢谢，伙计们，我没有意识到我需要这个。出于某种原因，我认为它会自行返回该值......不过，另一个问题。 binarySearch 方法似乎没有执行任何操作。在打印语句“使用二分搜索在随机数组中搜索 11”之后，什么也没有打印。

<小时/>

编辑2:我的binarySearch方法不起作用，因为我不小心为两个else语句设置了mid + 1(else if (key < array[mid]) 应该是mid - 1)。非常感谢大家!我添加了修复程序。

public class sortingSearching {

  public static boolean linearSearch (int [] array, int key) {
    for (int i = 0; i < array.length; i++) {
       if (array [i] == key)
           return true;
    }// end for
    return false;
}

public static int linearSearch2 (int [] array, int key) {
   for (int i = 0; i < array.length; i++) {
       if (array [i] == key)
        return i;
    }//end for
    return -1;
}//end linearSearch2

public static boolean binarySearch (int [] array, int key) {
  int left = 0;
    int right = array.length - 1;
    int mid = (left + right) /2;
       while (left <= right) {
           if (array[mid] == key)
               return true;
            else if ( key < array[mid])
               right = mid - 1;
            else 
               left = mid + 1;
            mid = (left + right) /2;
        } //end while
    return false;
}//end binarySearch

public static void printIntArray (int [] array) {
   for (int i = 0; i < array.length; i++) {
       if (i%10 == 0)
           System.out.println();
        System.out.print(array[i] + " ");
    } // end for
}

public static void selectionSort (int [] array) {
   for (int start = 0; start < array.length - 1; start ++) {
       int minI = start;
        for (int i = start + 1; i < array.length; i++)
           if (array[i] < array[start])
               minI = i;
       int temp = array[start];
    array[start] = array[minI];
       array[minI] = temp; 
    }//end for
   } //end selectionSort

public static void main (String args []) {
   int [] array = new int [20];
    for (int i =0; i < array.length; i++)
       array[i] = (int)((Math.random() * 100) + 1);

    //print the array using printArray  
    printIntArray(array);
    System.out.println();
  //use linearSearch to search for 30, 86, and 87
    System.out.println("Searching for 30 in the random array. If true is returned, " +
    "the value was found. If false was returned, the value was not found.");
      System.out.println(linearSearch(array, 30));
    System.out.println("Searching for 86 in the random array. If true is returned, " +
    "the value was found. If false was returned, the value was not found.");
       System.out.println(linearSearch(array, 86));
    System.out.println("Searching for 87 in the random array. If true is returned, " +
    "the value was found. If false was returned, the value was not found.");
       System.out.println(linearSearch(array, 87));
    //use linearSearch to locate the first occurrences of 25, 80, and 91
    System.out.println("Searching for the location of 25 in the random array. If -1 is " +
     "returned, the number was not found in the array.");
       System.out.println(linearSearch2(array, 25));
    System.out.println("Searching for the location of 80 in the random array. If -1 is " +
     "returned, the number was not found in the array.");
       System.out.println(linearSearch2(array, 80));
    System.out.println("Searching for the location of 91 in the random array. If -1 is " +
     "returned, the number was not found in the array.");
       System.out.println(linearSearch2(array, 91));
    //use selectionSort to sort the array
  selectionSort(array);
    //use binarySearch to search for 11, 28, 74, and 99
  System.out.println("Searching for 11 in the random array using binary search. If true is returned, " +
    "the value was found. If false was returned, the value was not found.");
       System.out.println(binarySearch (array, 11));
  System.out.println("Searching for 28 in the random array using binary search. If true is returned, " +
    "the value was found. If false was returned, the value was not found.");
       System.out.println(binarySearch (array, 28));
  System.out.println("Searching for 74 in the random array using binary search. If true is returned, " +
    "the value was found. If false was returned, the value was not found.");
       System.out.println(binarySearch (array, 74));
  System.out.println("Searching for 99 in the random array using binary search. If true is returned, " +
    "the value was found. If false was returned, the value was not found.");
       System.out.println(binarySearch (array, 99));
} //end main


} //end sortingSearching

此外，我很抱歉主方法中的所有打印语句都分散了注意力。我考虑过将它们删除以方便阅读，但我希望它与我运行时的完全一样。

Answer 1

linearSearch(array, 30);

他们确实会返回一些东西。但是对返回值做一些事情!

boolean value = linearSearch(array, 30);
System.out.println(value);

或者更简单:

System.out.println(linearSearch(array, 30));

响应您的编辑

您需要向1发起left。您正在执行整数除法，它永远不会达到零。因此，right 卡在 1 上，而 left 始终小于它。