Java.util.Arrays.binarySearch(char[] a, int fromIndex, int toIndex, char key)方法實例

描述

The java.util.Arrays.binarySearch(char[] a, int fromIndex, int toIndex, char key) method searches a range of the specified array of chars for the specified value using the binary search algorithm. The range must be sorted before making this call.If it is not sorted, the results are undefined.

聲明

Following is the declaration for java.util.Arrays.binarySearch() method

public static int binarySearch(char[] a, int fromIndex, int toIndex, char key)

參數

• a -- This is the array to be searched.

• fromIndex -- This is the index of the first element (inclusive) to be searched.

• toIndex -- This is the index of the last element (exclusive) to be searched.

• key -- This is the value to be searched for.

返回值

This method returns index of the search key, if it is contained in the array, else it returns (-(insertion point) - 1). The insertion point is the point at which the key would be inserted into the array; the index of the first element in the range greater than the key, or toIndex if all elements in the range are less than the specified key.

異常

• IllegalArgumentException -- if fromIndex > toIndex

• ArrayIndexOutOfBoundsException -- if fromIndex < 0 or toIndex > a.length

實例一

以下例子將告訴你如何使用 java.util.Arrays.binarySearch() method.

package gitbook.net;

import java.util.Arrays;

public class ArrayDemo {

   public static void main(String[] args) {

    // initializing unsorted char array
    char charArr[] = {'a', 'c', 'b', 'e','d'};

    // sorting array
    Arrays.sort(charArr);

    // let us print all the elements available in list
    System.out.println("The sorted char array is:");
    for (char number : charArr) {
      System.out.println("Number = " + number);
    }

    // entering the value to be searched
    char searchVal = 'e';

    // entering the range of index
    int retVal = Arrays.binarySearch(charArr,1,5,searchVal);

    System.out.println("The index of e is : " + retVal);
  }
}

編譯和執行以上程序，將得到以下的結果：

The sorted char array is:
Number = a
Number = b
Number = c
Number = d
Number = e
The index of e is : 4

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