StringBuilder class

A mutable sequence of characters.

Create StringBuilder object

ConstructorSummary
StringBuilder()Creates a string builder and an initial capacity of 16 characters.
StringBuilder(CharSequence seq)Creates a string builder from the specified CharSequence.
StringBuilder(int capacity)Creates a string builder with no characters in it and an initial capacity specified by the capacity argument.
StringBuilder(String str)Creates a string builder initialized to the contents of the specified string.

Append and insert value to StringBuilder

ReturnMethodSummary
StringBuilderappend(boolean b)Appends the string representation of the boolean argument to the sequence.
StringBuilderappend(char c)Appends the string representation of the char argument to this sequence.
StringBuilderappend(char[] str)Appends the string representation of the char array argument to this sequence.
StringBuilderappend(char[] str, int offset, int len)Appends the string representation of a subarray of the char array argument to this sequence.
StringBuilderappend(CharSequence s)Appends the specified character sequence to this Appendable.
StringBuilderappend(CharSequence s, int start, int end)Appends a subsequence of the specified CharSequence to this sequence.
StringBuilderappend(double d)Appends the string representation of the double argument to this sequence.
StringBuilderappend(float f)Appends the string representation of the float argument to this sequence.
StringBuilderappend(int i)Appends the string representation of the int argument to this sequence.
StringBuilderappend(long lng)Appends the string representation of the long argument to this sequence.
StringBuilderappend(Object obj)Appends the string representation of the Object argument.
StringBuilderappend(String str)Appends the specified string to this character sequence.
StringBuilderappend(StringBuffer sb)Appends the specified StringBuffer to this sequence.
StringBuilderappendCodePoint(int codePoint)Appends the string representation of the codePoint argument to this sequence.
StringBuilderinsert(int offset, boolean b)Inserts the string representation of the boolean argument into this sequence.
StringBuilderinsert(int offset, char c)Inserts the string representation of the char argument into this sequence.
StringBuilderinsert(int offset, char[] str)Inserts the string representation of the char array argument into this sequence.
StringBuilderinsert(int index, char[] str, int offset, int len)Inserts the string representation of a subarray of the str array argument into this sequence.
StringBuilderinsert(int dstOffset, CharSequence s)Inserts the specified CharSequence into this sequence.
StringBuilderinsert(int dstOffset, CharSequence s, int start, int end)Inserts a subsequence of the specified CharSequence into this sequence.
StringBuilderinsert(int offset, double d)Inserts the string representation of the double argument into this sequence.
StringBuilderinsert(int offset, float f)Inserts the string representation of the float argument into this sequence.
StringBuilderinsert(int offset, int i)Inserts the string representation of the second int argument into this sequence.
StringBuilderinsert(int offset, long l)Inserts the string representation of the long argument into this sequence.
StringBuilderinsert(int offset, Object obj)Inserts the string representation of the Object argument into this character sequence.
StringBuilderinsert(int offset, String str)Inserts the string into this character sequence.

Capacity and length

ReturnMethodMeaning
intcapacity()Returns the current capacity.
intlength()Returns the length (character count).
voidensureCapacity(int minimumCapacity)Ensures that the capacity is at least equal to the specified minimum.
voidsetLength(int newLength)Sets the length of the character sequence.
voidtrimToSize()Attempts to reduce storage used for the character sequence.

Search sub string

ReturnMethodMeaning
intindexOf(String str)Returns the index within this string of the first occurrence of the specified substring.
intindexOf(String str, int fromIndex)Returns the index within this string of the first occurrence of the specified substring, starting at the specified index.
intlastIndexOf(String str)Returns the index within this string of the rightmost occurrence of the specified substring.
intlastIndexOf(String str, int fromIndex)Returns the index within this string of the last occurrence of the specified substring.

Chars in StringBuilder

ReturnMethodMeaning
charcharAt(int index)Returns the char value in this sequence at the specified index.
voidsetCharAt(int index, char ch)The character at the specified index is set to ch.
voidgetChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)Characters are copied from this sequence into the destination character array dst.

Delete and replace and reverse

ReturnMethodMeaning
StringBuilderdelete(int start, int end)Removes the characters in a substring of this sequence.
StringBuilderdeleteCharAt(int index)Removes the char at the specified position in this sequence.
StringBuilderreplace(int start, int end, String str)Replaces the characters in a substring of this sequence with characters in the specified String.
StringBuilderreverse()Causes this character sequence to be replaced by the reverse of the sequence.

Get Sub string from StringBuilder

ReturnMethodMeaning
CharSequencesubSequence(int start, int end)Returns a new character sequence that is a subsequence of this sequence.
Stringsubstring(int start)Returns a new String that contains a subsequence of characters currently contained in this character sequence.
Stringsubstring(int start, int end)Returns a new String that contains a subsequence of characters currently contained in this sequence.

Convert StringBuilder to String

ReturnMethodMeaning
StringtoString()Returns a string representing the data in this sequence.
Revised from Open JDK source code
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