Java Arrays.binarySearch()方法用法及代碼示例

Arrays.binarySearch()是在Java中找到排序數組中元素的最簡單，最有效的方法

用法：

public static int binarySearch(data_type arr, data_type key )

其中data_type可以是任何原始數據類型：byte，char，double，int，float，short，long和Object。

描述：
使用二進製搜索算法在給定數據類型的指定數組中搜索指定值。在進行此調用之前，必須對數組進行排序(例如通過Arrays.sort()方法)。如果未排序，則結果不確定。如果數組包含具有指定值的多個元素，則不能保證將找到哪個元素。

參數：
arr-要搜索的數組
key–要搜索的值

返回：
搜索關鍵字的索引(如果包含在數組中)；否則，(-(插入點)-1)。插入點定義為將鍵插入數組的點：第一個元素的索引大於鍵，如果數組中的所有元素都小於指定的鍵，則為a.length。請注意，這保證了當且僅當找到 key 時，返回值才會> = 0。

例子：

Searching for 35 in byteArr[] = {10,20,15,22,35}
will give result as 4 as it is the index of 35

Searching for g in charArr[] = {'g','p','q','c','i'}
will give result as 1 as it is the index of 'g'

Searching for 22 in intArr[] = {10,20,15,22,35};
will give result as 3 as it is the index of 22

Searching for 1.5 in doubleArr[] = {10.2,15.1,2.2,3.5}
will give result as -1 as it is the insertion point of 1.5

Searching for 35.0 in floatArr[] = {10.2f,15.1f,2.2f,3.5f}
will give result as -5 as it is the insertion point of 35.0

Searching for 5 in shortArr[] = {10,20,15,22,35}
will give result as -1 as it is the insertion point of 5

// Java program to demonstrate working of Arrays. 
// binarySearch() in a sorted array. 
import java.util.Arrays; 
  
public class GFG 
{ 
    public static void main(String[] args) 
    { 
        byte byteArr[] = {10,20,15,22,35}; 
        char charArr[] = {'g','p','q','c','i'}; 
        int intArr[] = {10,20,15,22,35}; 
        double doubleArr[] = {10.2,15.1,2.2,3.5}; 
        float floatArr[] = {10.2f,15.1f,2.2f,3.5f}; 
        short shortArr[] = {10,20,15,22,35}; 
  
        Arrays.sort(byteArr); 
        Arrays.sort(charArr); 
        Arrays.sort(intArr); 
        Arrays.sort(doubleArr); 
        Arrays.sort(floatArr); 
        Arrays.sort(shortArr); 
  
        byte byteKey = 35; 
        char charKey = 'g'; 
        int intKey = 22; 
        double doubleKey = 1.5; 
        float floatKey = 35; 
        short shortKey = 5; 
  
        System.out.println(byteKey + " found at index = "
                           +Arrays.binarySearch(byteArr,byteKey)); 
        System.out.println(charKey + " found at index = "
                           +Arrays.binarySearch(charArr,charKey)); 
        System.out.println(intKey + " found at index = "
                           +Arrays.binarySearch(intArr,intKey)); 
        System.out.println(doubleKey + " found at index = "
                           +Arrays.binarySearch(doubleArr,doubleKey)); 
        System.out.println(floatKey + " found at index = "
                           +Arrays.binarySearch(floatArr,floatKey)); 
        System.out.println(shortKey + " found at index = "
                           +Arrays.binarySearch(shortArr,shortKey)); 
    } 
}

輸出：

35 found at index = 4
g found at index = 1
22 found at index = 3
1.5 found at index = -1
35.0 found at index = -5
5 found at index = -1

重要事項：

如果輸入列表未排序，則結果不確定。
如果有重複項，則不能保證將找到哪一個。

數組.binarysearch()與Java - Collections.binarySearch()用法及代碼示例
Arrays.binarysearch()適用於也可以是原始數據類型的數組。 Collections.binarysearch()適用於ArrayList和LinkedList之類的對象集合。

此方法有多種形式，其中我們還可以指定要搜索的數組範圍。我們將在後麵的文章中討論以及在Object數組中進行搜索。

相關用法

注：本文由純淨天空篩選整理自 Arrays.binarySearch() in Java with examples | Set 1。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。