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Golang strings.LastIndex() Function with Examples

Golang | strings.LastIndex() Function: Here, we are going to learn about the LastIndex() function of the strings package with its usages, syntax, and examples.
Submitted by IncludeHelp, on August 17, 2021

strings.LastIndex()

The LastIndex() function is an inbuilt function of strings package which is used to get the index of the last occurrence (instance) of the substring in a string. It accepts two parameters – string and substring and returns the last index, or returns -1 if the substring is not present in the string.

Syntax

func LastIndex(str, substr string) int

Parameters

• str : String in which we have to check the last index substring.
• substr : Substring to be checked in the string.

Return Value

The return type of the LastIndex() function is an int, it returns the index of the last occurrence (instance) of the substring in a string, or -1 if the substring is not present in the string.

Example 1

// Golang program to demonstrate the
// example of strings.LastIndex() Function

package main

import (
	"fmt"
	"strings"
)

func main() {
	fmt.Println(strings.LastIndex("Hello, world", "world"))
	fmt.Println(strings.LastIndex("abcdabba", "ab"))
	fmt.Println(strings.LastIndex("abcdabba", "ce"))
}

Output:

7
4
-1

Example 2

// Golang program to demonstrate the
// example of strings.LastIndex() Function

package main

import (
	"fmt"
	"strings"
)

func main() {
	var str string
	var substr string
	var index int

	str = "Hello, world!"
	substr = "world"

	index = strings.LastIndex(str, substr)
	if index >= 0 {
		fmt.Printf("Last index of %q in %q is %d.\n", substr, str, index)
	} else {
		fmt.Printf("%q does not found in %q.\n", substr, str)
	}

	str = "Hello, world!"
	substr = "l"

	index = strings.LastIndex(str, substr)
	if index >= 0 {
		fmt.Printf("Last index of %q in %q is %d.\n", substr, str, index)
	} else {
		fmt.Printf("%q does not found in %q.\n", substr, str)
	}

	str = "Hello! Hi! How are you?"
	substr = "H"

	index = strings.LastIndex(str, substr)
	if index >= 0 {
		fmt.Printf("Last index of %q in %q is %d.\n", substr, str, index)
	} else {
		fmt.Printf("%q does not found in %q.\n", substr, str)
	}

	str = "Hello! Hi! How are you?"
	substr = "am"

	index = strings.LastIndex(str, substr)
	if index >= 0 {
		fmt.Printf("Last index of %q in %q is %d.\n", substr, str, index)
	} else {
		fmt.Printf("%q does not found in %q.\n", substr, str)
	}
}

Output:

Last index of "world" in "Hello, world!" is 7.
Last index of "l" in "Hello, world!" is 10.
Last index of "H" in "Hello! Hi! How are you?" is 11.
"am" does not found in "Hello! Hi! How are you?".

Golang strings Package Functions »

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