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I'm trying to use substring function in java, but it keeps throwing an error, I want to know why ? the code seems to be good logically speaking but why it is throwing this error 

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1

What I've read in the documentation substring takes 2 parameter 

substring(whereIwantToStart,howManyCharactersToshow)

below is my code 

    String test = "160994";
    System.out.println(test.substring(2,1)); //output should be 09 why error?

Can someone explain me what is wrong ? please I need explanation. Thanks :)

user207421
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Valek
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    Hint: all Java library classes and methods are documented extremely well. Instead of just invoking a method, you should always always always first read that documentation. There is no point in calling methods without knowing what their parameters mean. – GhostCat Jun 02 '18 at 09:14
  • Example from the documentation: "hamburger".substring(4, 8) returns "urge" "smiles".substring(1, 5) returns "mile" – Abhijith S Jun 02 '18 at 09:18
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    Possible duplicate of [Java: substring index range](https://stackoverflow.com/questions/4570037/java-substring-index-range) – Abhijith S Jun 02 '18 at 09:21
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    Could you provide the document which said " substring takes 2 parameter substring(whereIwantToStart,howManyCharactersToshow) "? – John Jun 02 '18 at 09:21
  • This should help you work with substring indexes: https://stackoverflow.com/a/33600969 – Pshemo Jun 02 '18 at 09:23
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    You have to read the documentation carefully, but don't get frustrated, the practice make the master. A little tip: If you are using eclipse, you could press CTRL+space just before "test." to show content assist which provide context, documentation and completion alternatives. Good luck. – Rcordoval Jun 02 '18 at 09:29

6 Answers6

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See the doc:

public String substring(int beginIndex, int endIndex)

Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1. Thus the length of the substring is endIndex-beginIndex.

You need "160994".substring(2, 4) to get 09.

Community
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xingbin
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1

End index should be greater than the Start Index. To get output as '09', you should provide the end index as 4 test.substring(2,4);

Returns a new string that is a substring of this string. The
substring begins at the specified beginIndex and extends to the character at index endIndex - 1.

Thus the length of the substring is endIndex-beginIndex.

The StringIndexOutOfBoundsException will throw in below cases

  1. beginIndex < 0
  2. endIndex > value.length
  3. endIndex - beginIndex < 0
Thanigai Arasu
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1

For your required output use- 

System.out.println(test.substring(2,4));
Raj
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This is the format for the substring in java 

public String substring(int beginIndex, int endIndex)

you are specifying start from index 2 and end at index 1 , that's why it's throwing an exception index out of range.

To get the output as 09 you need 

 System.out.println(test.substring(2,4));

Appendix - Java Docs https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#substring(int,%20int)

Shubham Chopra
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public String substring(int startIndex, int endIndex): This method returns new String object containing the substring of the given string from specified startIndex to endIndex.

Let's understand the startIndex and endIndex by the code given below.

String s="hello";  
System.out.println(s.substring(0,2));

Output : he

Notice :

endIndex > startIndex

in your case : change between 1 and 2 place to 

String test = "160994";
System.out.println(test.substring(2, 4)); //output should be 09

Output : 09

Abdo Bmz
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String test = "160994";

System.out.println(test.substring(2,1));

Substring means (beginIndex, endIndex) and endIndex Should be larger than beginIndex.and your value(09) should be stay between beninIndex(which is starting index) and endIndex(Which is last index).

and you have taken endIndex 1 so you are geting the Error because your beginIndex is larger than endIndex.

if you want to get Ans. 09 then you should have to put endIndex 4.

Line will be:-System.out.println(test.substring(2,4));

Samim Aktar
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