Java数组中具有重复值的indexOf（）

我试图打印此数组中每个值的索引值

    Integer[] i = { 0, 2, 3, 4, 4 };
    for (int each : i) {
      System.out.print(Arrays.asList(i).indexOf(each) + " ");
    }

现在，我想让它说0，1，2，3，4，而不是0，1，2，3，3

---

要获得每个特定索引，而不是每个值的“第一个匹配”，我需要更改什么？如果列表中有重复的值，则将在实现中返回第一个匹配值。要解决此问题，您可以创建一个副本数组，当在副本中找到值时，将其替换为null

下次重复的值将找不到第一个重复项，并将返回下一个索引

Integer[] i = {0,2,3,4,4};
Integer[] copy = new Integer[i.length];
System.arraycopy( i, 0, copy, 0, i.length );

        for (int each : i) {
            int index = Arrays.asList(copy).indexOf(each);
            System.out.print(index + " ");
            copy[index] = null;
        }

输出：01 2 3 4

---

当然，现在您可以对初始数组重新排序，它仍然会返回正确的索引

不确定您试图用代码实现什么，但如果您想打印数组的所有索引，而不是值，您可以这样做

Integer[] i = {0,2,3,4,4};
for (int index = 0; index < i.length; index++) 
{
    System.out.print(index + " ");
}

如果要获取数组中特定项的索引，可以执行以下操作：

public static void main(String[] args){

    // Create example Arrays
    Integer[] arrayOfIntegers = {1,2,3,4,5};
    String[] arrayOfStrings = {"A", "B", "C", "D",};

    /******Test*******/
    // what is the index of Integer 2 in the arrayOfIntegers
    System.out.println(getIndex(arrayOfIntegers, 2));

    // what is the index of String "C" in the arrayOfStrings
    System.out.println(getIndex(arrayOfStrings, "C"));

    // what is the index of String "X" in the arrayOfIStrings
    // which doesn't exist (expected value is -1)
    System.out.println(getIndex(arrayOfStrings, "X"));  
}

/**
 * This method to return the index of a given Object in
 * the array. It returns - 1 if doesn't exist
 * @param array
 * @param obj
 */
public static int getIndex(Object[] array, Object obj){
    for(int i=0; i<array.length; i++){
        if(obj.equals(array[i])){
            return i;
        }
    }
    return -1;
}

/**
* This method returns all indices of a given Object 
* in an ArrayList (which will be empty if did not found any)
* @param array
* @param obj
*/
public static ArrayList<Integer> getIndices(Object[] array, Object obj){
    ArrayList<Integer> indices = new ArrayList<Integer>();
    for(int i=0; i<array.length; i++){
        if(obj.equals(array[i])){
            indices.add(i);
        }
    }
    return indices;
}

此外，如果要返回数组中重复项的所有索引，可以执行以下操作：

public static void main(String[] args){

    // Create example Arrays
    Integer[] arrayOfIntegers = {1,2,3,4,5};
    String[] arrayOfStrings = {"A", "B", "C", "D",};

    /******Test*******/
    // what is the index of Integer 2 in the arrayOfIntegers
    System.out.println(getIndex(arrayOfIntegers, 2));

    // what is the index of String "C" in the arrayOfStrings
    System.out.println(getIndex(arrayOfStrings, "C"));

    // what is the index of String "X" in the arrayOfIStrings
    // which doesn't exist (expected value is -1)
    System.out.println(getIndex(arrayOfStrings, "X"));  
}

/**
 * This method to return the index of a given Object in
 * the array. It returns - 1 if doesn't exist
 * @param array
 * @param obj
 */
public static int getIndex(Object[] array, Object obj){
    for(int i=0; i<array.length; i++){
        if(obj.equals(array[i])){
            return i;
        }
    }
    return -1;
}

/**
* This method returns all indices of a given Object 
* in an ArrayList (which will be empty if did not found any)
* @param array
* @param obj
*/
public static ArrayList<Integer> getIndices(Object[] array, Object obj){
    ArrayList<Integer> indices = new ArrayList<Integer>();
    for(int i=0; i<array.length; i++){
        if(obj.equals(array[i])){
            indices.add(i);
        }
    }
    return indices;
}

---

我不知道你想得到什么，如果你一次迭代一个数组，从逻辑上讲，每次迭代的索引将与你的I值相同…@Aominèah，谢谢你的澄清。