String & Math Methods

Hello everyone!  We will be discussing a very important topic which is String & Math Methods. 

String Methods

In Java variables post, String is defined as one of the most used variables and defined like following;

String – text, such as “Hi”. String values need double quotes and String keyword should start with a capital letter

So basically, String is a variable with characters surrounded by double quotes (“  “). 

The main function of the String variable is to store the text and  it contains built-in  methods that can perform certain operations. 

String variables can be combined with different methods.  Those are known String methods. 

Examples:

Now look at the below table for different String methods.

Keyword	Method	Description
char	charAt(int index)	Returns the char value at the specified index.
int	codePointAt(int index)	Returns the character (Unicode code point) at the specified index.
int	codePointBefore(int index)	Returns the character (Unicode code point) before the specified index.
int	codePointCount(int beginIndex, int endIndex)	Returns the number of Unicode code points in the specified text range of this String.
int	compareTo(String anotherString)	Compares two strings lexicographically.
int	compareToIgnoreCase(String str)	Compares two strings lexicographically, ignoring case differences.
String	concat(String str)	Concatenates the specified string to the end of this string.
boolean	contains(CharSequence s)	Returns true if and only if this string contains the specified sequence of char values.
boolean	contentEquals(CharSequence cs)	Compares this string to the specified CharSequence.
boolean	contentEquals(StringBuffer sb)	Compares this string to the specified StringBuffer.
static String	copyValueOf(char[] data)	Returns a String that represents the character sequence in the array specified.
static String	copyValueOf(char[] data, int offset, int count)	Returns a String that represents the character sequence in the array specified.
boolean	endsWith(String suffix)	Tests if this string ends with the specified suffix.
boolean	equals(Object anObject)	Compares his string to the specified object.
boolean	equalsIgnoreCase(String anotherString)	Compares this String to another String, ignoring case considerations.
static String	format(Locale l, String format, Object… args)	Returns a formatted string using the specified locale, format string, and arguments.
static String	format(String format, Object… args)	Returns a formatted string using the specified format string and arguments.
byte[]	getBytes()	Encodes this String into a sequence of bytes using the platform’s default charset, storing the result into a new byte array.
byte[]	getBytes(Charset charset)	Encodes this String into a sequence of bytes using the given charset, storing the result into a new byte array.
void	getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)	Deprecated. This method does not properly convert characters into bytes. As of JDK 1.1, the preferred way to do this is via the getBytes() method, which uses the platform’s default charset.
byte[]	getBytes(String charsetName)	Encodes this String into a sequence of bytes using the named charset, storing the result into a new byte array.
void	getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)	Copies characters from this string into the destination character array.
int	hashCode()	Returns a hash code for this string.
int	indexOf(int ch)	Returns the index within this string of the first occurrence of the specified character.
int	indexOf(int ch, int fromIndex)	Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index.
int	indexOf(String str)	Returns the index within this string of the first occurrence of the specified substring.
int	indexOf(String str, int fromIndex)	Returns the index within this string of the first occurrence of the specified substring, starting at the specified index.
String	intern()	Returns a canonical representation for the string object.
boolean	isEmpty()	Returns true if, and only if, length() is 0.
int	lastIndexOf(int ch)character.	Returns the index within this string of the last occurrence of the specified
int	lastIndexOf(int ch, int fromIndex)	Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index.
int	lastIndexOf(String str)	Returns the index within this string of the last occurrence of the specified substring.
int	lastIndexOf(String str, int fromIndex)	Returns the index within this string of the last occurrence of the specified substring, searching backward starting at the specified index.
int	length()	Returns the length of this string.
boolean	matches(String regex)	Tells whether or not this string matches the given regular expression.
int	offsetByCodePoints(int index, int codePointOffset)	Returns the index within this String that is offset from the given index by codePointOffset code points.
boolean	regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)	Tests if two string regions are equal.
boolean	regionMatches(int toffset, String other, int ooffset, int len)	Tests if two string regions are equal.
String	replace(char oldChar, char newChar)	Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.
String	replace(CharSequence target, CharSequence replacement)	Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence.
String	replaceAll(String regex, String replacement)	Replaces each substring of this string that matches the given regular expression with the given replacement.
String	replaceFirst(String regex, String replacement)	Replaces the first substring of this string that matches the given regular expression with the given replacement.
String[]	split(String regex)	Splits this string around matches of the given regular expression.
String[]	split(String regex, int limit)	Splits this string around matches of the given regular expression.
boolean	startsWith(String prefix)	Tests if this string starts with the specified prefix.
boolean	startsWith(String prefix, int toffset)	Tests if the substring of this string beginning at the specified index starts with the specified prefix.
CharSequence	subSequence(int beginIndex, int endIndex)	Returns a new character sequence that is a subsequence of this sequence.
String	substring(int beginIndex)	Returns a new string that is a substring of this string.
String	substring(int beginIndex, int endIndex)	Returns a new string that is a substring of this string.
char[]	toCharArray()	Converts this string to a new character array.
String	toLowerCase()	Converts all of the characters in this String to lowercase using the rules of the default locale.
String	toLowerCase(Locale locale)	Converts all of the characters in this String to lowercase using the rules of the given Locale.
String	toString()	This object (which is already a string!) is itself returned.
String	toUpperCase()	Converts all of the characters in this String to upper case using the rules of the default locale.
String	toUpperCase(Locale locale)	Converts all of the characters in this String to upper case using the rules of the given Locale.
String	trim()	Returns a copy of the string, with leading and trailing whitespace omitted.
static String	valueOf(boolean b)	Returns the string representation of the boolean argument.
static String	valueOf(char c)	Returns the string representation of the char argument.
static String	valueOf(char[] data)	Returns the string representation of the char array argument.
static String	valueOf(char[] data, int offset, int count)	Returns the string representation of a specific subarray of the char array argument.
static String	valueOf(double d)	Returns the string representation of the double argument.
static String	valueOf(float f)	Returns the string representation of the float argument.
static String	valueOf(int i)	Returns the string representation of the int argument.
static String	valueOf(long l)	Returns the string representation of the long argument.
static String	valueOf(Object obj)	Returns the string representation of the Object argument.

Math Methods

Math methods are used to perform advanced mathematics that are harder to do by simple keys.

Examples:

Now look below for a table for different math methods.

Keyword	Method	Description
static double	abs(double a)	Returns the absolute value of a double value.
static float	abs(float a)	Returns the absolute value of a float value.
static int	abs(int a)	Returns the absolute value of an int value.
static long	abs(long a)	Returns the absolute value of a long value.
static double	acos(double a)	Returns the arc cosine of a value; the returned angle is in the range 0.0 through pi.
static double	asin(double a)	Returns the arc sine of a value; the returned angle is in the range -pi/2 through pi/2.
static double	atan(double a)	Returns the arc tangent of a value; the returned angle is in the range -pi/2 through pi/2.
static double	atan2(double y, double x)	Returns the angle theta from the conversion of rectangular coordinates (x, y) to polar coordinates (r, theta).
static double	cbrt(double a)	Returns the cube root of a double value.
static double	ceil(double a)	Returns the smallest (closest to negative infinity) double value that is greater than or equal to the argument and is equal to a mathematical integer.
static double	copySign(double magnitude, double sign)	Returns the first floating-point argument with the sign of the second floating-point argument.
static float	copySign(float magnitude, float sign)	Returns the first floating-point argument with the sign of the second floating-point argument.
static double	cos(double a)	Returns the trigonometric cosine of an angle.
static double	cosh(double x)	Returns the hyperbolic cosine of a double value.
static double	exp(double a)	Returns Euler’s number e raised to the power of a double value.
static double	expm1(double x)	Returns ex -1.
static double	floor(double a)	Returns the largest (closest to positive infinity) double value that is less than or equal to the argument and is equal to a mathematical integer.
static int	getExponent(double d)	Returns the unbiased exponent used in the representation of a double.
static int	getExponent(float f)	Returns the unbiased exponent used in the representation of a float.
static double	hypot(double x, double y)	Returns sqrt(x2 +y2) without intermediate overflow or underflow.
static double	IEEEremainder(double f1, double f2)	Computes the remainder operation on two arguments as prescribed by the IEEE 754 standard.
static double	log(double a)	Returns the natural logarithm (base e) of a double value.
static double	log10(double a)	Returns the base 10 logarithm of a double value.
static double	log1p(double x)	Returns the natural logarithm of the sum of the argument and 1.
static double	max(double a, double b)	Returns the greater of two double values.
static float	max(float a, float b)	Returns the greater of two float values.
static int	max(int a, int b)	Returns the greater of two int values.
static long	max(long a, long b)	Returns the greater of two long values.
static double	min(double a, double b)	Returns the smaller of two double values.
static float	min(float a, float b)	Returns the smaller of two float values.
static int	min(int a, int b)	Returns the smaller of two int values.
static long	min(long a, long b)	Returns the smaller of two long values.
static double	nextAfter(double start, double direction)	Returns the floating-point number adjacent to the first argument in the direction of the second argument.
static float	nextAfter(float start, double direction)	Returns the floating-point number adjacent to the first argument in the direction of the second argument.
static double	nextUp(double d)	Returns the floating-point value adjacent to d in the direction of positive infinity.
static float	nextUp(float f)	Returns the floating-point value adjacent to f in the direction of positive infinity.
static double	pow(double a, double b)	Returns the value of the first argument raised to the power of the second argument.
static double	random()	Returns a double value with a positive sign, greater than or equal to 0.0 and less than 1.0.
static double	rint(double a)	Returns the double value that is closest in value to the argument and is equal to a mathematical integer.
static long	round(double a)	Returns the closest long to the argument, with ties rounding up.
static int	round(float a)	Returns the closest int to the argument, with ties rounding up.
static double	scalb(double d, int scaleFactor)	Return d × 2scaleFactor rounded as if performed by a single correctly rounded floating-point multiply to a member of the double value set.
static float	scalb(float f, int scaleFactor)	Return f × 2scaleFactor rounded as if performed by a single correctly rounded floating-point multiply to a member of the float value set.
static double	signum(double d)	Returns the signum function of the argument; zero if the argument is zero, 1.0 if the argument is greater than zero, -1.0 if the argument is less than zero.
static float	signum(float f)	Returns the signum function of the argument; zero if the argument is zero, 1.0f if the argument is greater than zero, -1.0f if the argument is less than zero.
static double	sin(double a)	Returns the trigonometric sine of an angle.
static double	sinh(double x)	Returns the hyperbolic sine of a double value.
static double	sqrt(double a)	Returns the correctly rounded positive square root of a double value.
static double	tan(double a)	Returns the trigonometric tangent of an angle.
static double	tanh(double x)	Returns the hyperbolic tangent of a double value.
static double	toDegrees(double angrad)	Converts an angle measured in radians to an approximately equivalent angle measured in degrees.
static double	toRadians(double angdeg)	Converts an angle measured in degrees to an approximately equivalent angle measured in radians.
static double	ulp(double d)	Returns the size of an ulp of the argument.
static float	ulp(float f)	Returns the size of an ulp of the argument.

Please look at the examples and practice by using Netbeans. If you like, please post your examples in comments.