Substring start end java

Class StringBuilder

A mutable sequence of characters. This class provides an API compatible with StringBuffer , but with no guarantee of synchronization. This class is designed for use as a drop-in replacement for StringBuffer in places where the string buffer was being used by a single thread (as is generally the case). Where possible, it is recommended that this class be used in preference to StringBuffer as it will be faster under most implementations.

The principal operations on a StringBuilder are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string builder. The append method always adds these characters at the end of the builder; the insert method adds the characters at a specified point.

For example, if z refers to a string builder object whose current contents are » start «, then the method call z.append(«le») would cause the string builder to contain » startle «, whereas z.insert(4, «le») would alter the string builder to contain » starlet «.

In general, if sb refers to an instance of a StringBuilder , then sb.append(x) has the same effect as sb.insert(sb.length(), x) .

Every string builder has a capacity. As long as the length of the character sequence contained in the string builder does not exceed the capacity, it is not necessary to allocate a new internal buffer. If the internal buffer overflows, it is automatically made larger.

Instances of StringBuilder are not safe for use by multiple threads. If such synchronization is required then it is recommended that StringBuffer be used.

Unless otherwise noted, passing a null argument to a constructor or method in this class will cause a NullPointerException to be thrown.

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Class StringBuilder

A mutable sequence of characters. This class provides an API compatible with StringBuffer , but with no guarantee of synchronization. This class is designed for use as a drop-in replacement for StringBuffer in places where the string buffer was being used by a single thread (as is generally the case). Where possible, it is recommended that this class be used in preference to StringBuffer as it will be faster under most implementations.

The principal operations on a StringBuilder are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string builder. The append method always adds these characters at the end of the builder; the insert method adds the characters at a specified point.

For example, if z refers to a string builder object whose current contents are » start «, then the method call z.append(«le») would cause the string builder to contain » startle «, whereas z.insert(4, «le») would alter the string builder to contain » starlet «.

In general, if sb refers to an instance of a StringBuilder , then sb.append(x) has the same effect as sb.insert(sb.length(), x) .

Every string builder has a capacity. As long as the length of the character sequence contained in the string builder does not exceed the capacity, it is not necessary to allocate a new internal buffer. If the internal buffer overflows, it is automatically made larger.

Instances of StringBuilder are not safe for use by multiple threads. If such synchronization is required then it is recommended that StringBuffer be used.

Unless otherwise noted, passing a null argument to a constructor or method in this class will cause a NullPointerException to be thrown.

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Java String substring() Method with examples

The substring() method is used to get a substring from a given string. This is a built-in method of string class, it returns the substring based on the index values passed to this method. For example: “Beginnersbook”.substring(9) would return “book” as a substring.

This method has two variants, one is where you just specify the start index and in the other variant, you can specify both start and end indexes.

String substring() method variants

There are two variants of substring method in Java.

1. Only the beginIndex:

String substring(int beginIndex)

Returns the substring starting from the specified index beginIndex till the last character of the string.

For example: «Chaitanya».substring(2) would return «aitanya» . The beginIndex is inclusive, that is why the character present at the index 2 is included in the substring.

This method throws IndexOutOfBoundsException If the beginIndex is less than zero or greater than the length of String (beginIndex <0||>length of String).

2. Both beginIndex and endIndex:

String substring(int beginIndex, int endIndex)

Returns a substring starting from specified beginIndex till the character present at endIndex – 1. Thus the length of the substring is endIndex-beginIndex. In other words you can say that beginIndex is inclusive and endIndex is exclusive while getting the substring.

For example: «Chaitanya».substring(2,5) would return «ait» .

It throws IndexOutOfBoundsException If the beginIndex is less than zero OR beginIndex > endIndex OR endIndex is greater than the length of String.

Java String substring() examples

Now that we understand the basics of substring() method, let’s take few examples to understand the usage of this method.

1. Basic substring example demonstrates both the variants of this method

Before we start to see some interesting substring method examples, let’s start with a simple example that demonstrates the usage of this method.

Output:

Note: The returned substring length is always endIndex-beginIndex, In our example beginIndex is 3 and endIndex is 7, thus the length of returned substring should be 7-3 = 4.

2. Get a substring between two delimiters

We are finding the indexes of delimiters in the string using indexOf() method. Once we have the indexes of delimiters, we are calling substring method to find the substring between these delimiters.

Note: The method is called like this: substring(start + 1, end), here start index is +1 because, we want to get the substring after the delimiter position, however the end index is not +1 because end index is not inclusive in substring method.

Similarly you can use the same logic to get the substring between two characters:

3. Get a substring between two given strings

This is another interesting example. Here we have a string and we want to get a substring between two strings “Beginners” and “com”. To do this, we have searched the index of first string using indexOf() and added the length of this string, this is because indexOf() gives the index of first character of the string but we want to start reading after the end of string “Beginners”.

Similarly, we found the starting index of second string “com” and get the substring between these indexes using substring method.

4. Remove first and last character from a string

In this program, we are using substring() method to exclude first and last character from the string.

• str.substring(1): This excludes first character as the index 0 character (first character) is excluded.
• substring(0, str.length()-1): This excludes last character as the length() method returns the length of the string and when we provide str.length()-1 as the endIndex, it excludes last character.

Output:

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Comments

I thought it would be ” jump” if we consider the space before the word “jumps” as a character.
As its explained above the example , “chaitanya”.substring(2,5) and the result is “a(2)i(3)t(4)”, so the fifth character isn’t taken ?

also count space ,secondly 20 end at “s”,so java show less one character.so result is jump.
Example:
abc
012
(0,1) show just a exclusive end point.

When using .substring(x,y), the x index is inclusive and y index is exclusive, therefore it is “jump”.

may want to review the java documentation (the key here is how the end index is handled: as value-1, or in other words “exclusively”): 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.
Examples:
“hamburger”.substring(4, 8) returns “urge”
“smiles”.substring(1, 5) returns “mile”
Parameters:
beginIndex – the beginning index, inclusive.
endIndex – the ending index, exclusive.
Returns:
the specified substring.
Throws:
IndexOutOfBoundsException – if the beginIndex is negative, or endIndex is larger than the length of this String object, or beginIndex is larger than endIndex. see: https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#substring(int,%20int)

Most computer languages for many years used a start index and a length as the parameters. For some reason Java decided to use a start and end index that actually returns the characters from start to end – 1. Personally I think this is a horrible implementation of this command, seems like a massive brain stress by the creators of Java. Now that Java is so popular there are 2 major ways this function works now that this stupid implementation has been repeated in several other languages.

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