Java字符串indexOf（）

灰太狼 2023-10-04 10:07 58阅读 0赞

## Java字符串indexOf（） ##

的**Java字符串的indexOf（）**方法返回给定的字符数值或子字符串的索引。如果找不到，则返回-1。索引计数器从零开始。

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Java中有4种indexOf方法。

<table> 
 <tbody> 
 <tr> 
 <th style="text-align:left;vertical-align:top;">&nbsp;</th> 
 <th style="text-align:left;vertical-align:top;">方法</th> 
 <th style="text-align:left;vertical-align:top;">描述</th> 
 </tr> 
 <tr> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">1</td> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">int indexOf（int ch）</td> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">返回给定char值的索引位置</td> 
 </tr> 
 <tr> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">2</td> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">int indexOf（int ch，int fromIndex）</td> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">返回给定char值和索引的索引位置</td> 
 </tr> 
 <tr> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">3</td> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">int indexOf(String substring)</td> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">返回给定子字符串的索引位置</td> 
 </tr> 
 <tr> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">4</td> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">int indexOf(String substring, int fromIndex)</td> 
 <td style="border-color:#c7ccbe;margin-left:20px;text-align:left;vertical-align:top;">返回给定子串的索引位置，并从索引返回</td> 
 </tr> 
 </tbody> 
</table>

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#### 参数 ####

**ch**：char值，即单个字符，例如“ a”

**fromIndex**：从此处获取char值或子字符串的索引的索引位置

**substring**：要在此字符串中搜索的子字符串

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#### 返回 ####

字符串的索引

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### Java String indexOf（）方法示例 ###

1.  public class IndexOfExample\{
2.  public static void main(String args\[\])\{
3.  String s1="this is index of example";
4.  //passing substring
5.  int index1=s1.indexOf("is");//returns the index of is substring
6.  int index2=s1.indexOf("index");//returns the index of index substring
7.  System.out.println(index1+" "+index2);//2 8
8.  
9.  //passing substring with from index
10. int index3=s1.indexOf("is",4);//returns the index of is substring after 4th index
11. System.out.println(index3);//5 i.e. the index of another is
12. 
13. //passing char value
14. int index4=s1.indexOf('s');//returns the index of s char value
15. System.out.println(index4);//3
16. \}\}

2 8
    5
    3

### Java String indexOf（String substring）方法示例 ###

此方法将子字符串作为参数，并返回该子字符串的第一个字符的索引。

1.  public class IndexOfExample2 \{
2.  public static void main(String\[\] args) \{
3.  String s1 = "This is indexOf method";
4.  // Passing Substring
5.  int index = s1.indexOf("method"); //Returns the index of this substring
6.  System.out.println("index of substring "+index);
7.  \}
8.  
9.  \}

index of substring 16

### Java字符串indexOf（String substring，int fromIndex）方法示例 ###

此方法将子字符串和索引作为参数，并返回在给定*fromIndex*之后出现的第一个字符的索引。

1.  public class IndexOfExample3 \{
2.  public static void main(String\[\] args) \{
3.  String s1 = "This is indexOf method";
4.  // Passing substring and index
5.  int index = s1.indexOf("method", 10); //Returns the index of this substring
6.  System.out.println("index of substring "+index);
7.  index = s1.indexOf("method", 20); // It returns -1 if substring does not found
8.  System.out.println("index of substring "+index);
9.  \}
10. \}

index of substring 16
    index of substring -1

### Java字符串indexOf（int char，int fromIndex）方法示例 ###

此方法将char和index作为参数，并返回在给定*fromIndex*之后出现的第一个字符的索引。

1.  public class IndexOfExample4 \{
2.  public static void main(String\[\] args) \{
3.  String s1 = "This is indexOf method";
4.  // Passing char and index from
5.  int index = s1.indexOf('e', 12); //Returns the index of this char
6.  System.out.println("index of char "+index);
7.  \}
8.  \}
9.

index of char 17