如何使用泛型方法搜索各种类型的数组中的特定变量？

Question

我试图在各种类型的数组中返回一个特定的变量，我只能使用泛型方法。但是，当我尝试执行搜索方法时，我不断收到此错误。有没有人可以给我一些想法你如何解决它？

我正在使用drjava。

这是调用语句：

 System.out.printf( "%nThe item returned from integerArray is: %s",
                      returnItem( integerArray,
                                  2 ) );

  System.out.printf( "%nThe item returned from doubleArray is: %s",
                      returnItem( doubleArray,
                                  2 ) );

  System.out.printf( "%nThe item returned from characterArray is: %s",
                      returnItem( characterArray,
                                  2 ) );

  System.out.printf( "%nThe item returned from petArray is: %s",
                      returnItem( petArray,
                                  2 ) );

这是我的搜索方法：

public static < T> int returnItem( T[ ] inputArray, int key ){

        // ERROR: incompatible types: T cannot be converted to int

    for ( int element : inputArray ){

        if( key == element ){

           return element;
       }
     }
       return -1;


} // end method returnItem 

从integerArray返回的项是：3

integerArray返回的项目是：3.3

从integerArray返回的项是：L

Answer 1

@Noone，我建议你在construtor中创建一个具有预期数据类型作为参数和arry time作为参数的类。然后您的通用退货项目按键或按项目返回可以世界。

如果不是太多。考虑我的实现如下：

public final class SearchAnyArray<T> {

    T[] inputArray;

    public SearchAnyArray(final String[] stringArray) {
        inputArray = (T[]) stringArray;
    }

    public SearchAnyArray(final int[] integerPrimitives) {
        Integer[] ints = new Integer[integerPrimitives.length];
        for (int x = 0; x < integerPrimitives.length; x++) {
            ints[x] = integerPrimitives[x];
        }
        inputArray = (T[]) ints;
    }

    public SearchAnyArray(final double[] doublePrimitives) {
        Double[] doubles = new Double[doublePrimitives.length];
        for (int x = 0; x < doublePrimitives.length; x++) {
            doubles[x] = doublePrimitives[x];
        }
        inputArray = (T[]) doubles;
    }

    public SearchAnyArray(char[] charPrimitives) {
        Character[] chars = new Character[charPrimitives.length];
        for (int x = 0; x < charPrimitives.length; x++) {
            chars[x] = charPrimitives[x];
        }
        inputArray = (T[]) chars;
    }

    public int returnItemIndex(T key) {
        for (int x = 0; x < inputArray.length; x++) {
            if (inputArray[x].equals(key)) {
                return x;
            }
        }
        return -1;
    }

    public T returnItem(int index) {
        if (index < 0 || index > (inputArray.length - 1)) {
            throw new ArrayIndexOutOfBoundsException("Invalid key ");
        }
        return inputArray[index];
    }

    public static void main(String[] args) {
        int[] a = {1, 4, 3, 9};
        double[] d = {1.0, 4.1, 3.3, 9.4};
        char[] c = "ALLOWEDforReal".toCharArray();
        String[] s = {"Any", "How", "Is", "a", "goal"};
        System.out.println(new SearchAnyArray<>(a).returnItem(2));
        System.out.println(new SearchAnyArray<>(d).returnItem(2));
        System.out.println(new SearchAnyArray<>(c).returnItem(2));
        System.out.println(new SearchAnyArray<>(s).returnItem(2));

        System.out.println(new SearchAnyArray<>(a).returnItemIndex(3));
        System.out.println(new SearchAnyArray<>(d).returnItemIndex(3.3));
        System.out.println(new SearchAnyArray<>(c).returnItemIndex('L'));
        System.out.println(new SearchAnyArray<>(s).returnItemIndex("Is"));

    }
}```