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Java - String indexOf() method example
5 points
Simple example:
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String text = "Here we are";2
int index = text.indexOf("H"); // 03
4
System.out.println( text.indexOf("H") ); // 05
System.out.println( text.indexOf("e") ); // 16
System.out.println( text.indexOf("r") ); // 27
System.out.println( text.indexOf(" ") ); // 48
System.out.println( text.indexOf("we") ); // 59
System.out.println( text.indexOf("are") ); // 8In this post we cover usage of String indexOf() method with simple code examples.
Definition:
We use Java String indexOf() method to find index of specified substring or char in given String.
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public class Example1 {2
3
public static void main(String[] args) {4
5
String text = "Here we are";6
int index = text.indexOf("we");7
System.out.println(index); // 58
}9
}Output:
xxxxxxxxxx1
5Why indexOf() method printed index 5? Explanation below.
Why indexOf() method printed index 5?
Below code prints indexes of each character.
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public class IndexExplanation {2
3
public static void main(String[] args) {4
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String text = "Here we are, we";6
for (int i = 0; i < text.length(); i++) {7
System.out.println("index: " + i + ", char: " + text.charAt(i));8
}9
}10
}Output:
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index: 0, char: H2
index: 1, char: e3
index: 2, char: r4
index: 3, char: e5
index: 4, char:6
index: 5, char: w7
index: 6, char: e8
index: 7, char:9
index: 8, char: a10
index: 9, char: r11
index: 10, char: e12
index: 11, char: ,13
index: 12, char:14
index: 13, char: w15
index: 14, char: eAnother short explanation of index
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// index: 0123456789..2
String text = "Here we are";3
// index of 'we' is 5xxxxxxxxxx1
public class Example3 {2
3
public static void main(String[] args) {4
5
String text = "Here we are, we";6
int index = text.indexOf("we", 6);7
System.out.println(index); // 138
}9
}Output:
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13xxxxxxxxxx1
public class Example4 {2
3
public static void main(String[] args) {4
5
String text = "Here we are";6
int index = text.indexOf('w');7
System.out.println(index); // 58
}9
}Output:
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5xxxxxxxxxx1
public class Example5 {2
3
public static void main(String[] args) {4
5
String text = "Here we are, we";6
int index = text.indexOf('w', 6);7
System.out.println(index); // 138
}9
}Output:
xxxxxxxxxx1
13Java provides 4 versions of indexOf with different parameters:
-
public int indexOf(String str) -
public int indexOf(String str, int fromIndex) -
public int indexOf(int ch) -
public int indexOf(int ch, int fromIndex)
The most popular version of indexOf() method is
public int indexOf(String str)
