Package tech.tablesaw.util

Class StringUtils

java.lang.Object

tech.tablesaw.util.StringUtils

public class StringUtils
extends Object

Operations on String that are null safe.

StringUtils handles null input Strings quietly. That is to say that a null input will return null. Where a boolean or int is being returned details vary by method.

A side effect of the null handling is that a NullPointerException should be considered a bug in StringUtils.

Methods in this class give sample code to explain their operation. The symbol * is used to indicate any input including null.

#ThreadSafe#

Since:

1.0

See Also:

• String

Method Summary

Modifier and Type	Method	Description
static String	abbreviate(String str, String abbrevMarker, int maxWidth)	Abbreviates a String using ellipses.
static String	capitalize(String str)	Capitalizes a String changing the first character to title case as per Character.toTitleCase(int).
static boolean	isAllLowerCase(String cs)	Checks if the CharSequence contains only lowercase characters.
static boolean	isAllUpperCase(String cs)	Checks if the CharSequence contains only uppercase characters.
static boolean	isAlpha(String cs)	Checks if the CharSequence contains only Unicode letters.
static boolean	isAlphanumeric(String cs)	Checks if the CharSequence contains only Unicode letters or digits.
static boolean	isNumeric(String cs)	Checks if the CharSequence contains only Unicode digits.
static int	length(CharSequence cs)	Gets a CharSequence length or 0 if the CharSequence is null.
static String	removeZeroDecimal(String str)	Removes all trailing zero decimals from the given String, assuming all decimals are zero and any zero decimals actually exist.
static String	repeat(String str, int repeat)	Repeat a String repeat times to form a new String.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

repeat

public static String repeat(String str,
 int repeat)

Repeat a String repeat times to form a new String.

 StringUtils.repeat(null, 2) = null
 StringUtils.repeat("", 0)   = ""
 StringUtils.repeat("", 2)   = ""
 StringUtils.repeat("a", 3)  = "aaa"
 StringUtils.repeat("ab", 2) = "abab"
 StringUtils.repeat("a", -2) = ""
 

Parameters:

str - the String to repeat, may be null

repeat - number of times to repeat str, negative treated as zero

Returns:

a new String consisting of the original String repeated, null if null String input

length

public static int length(CharSequence cs)

Gets a CharSequence length or 0 if the CharSequence is null.

Parameters:

cs - a CharSequence or null

Returns:

CharSequence length or 0 if the CharSequence is null.

Since:

2.4, 3.0 Changed signature from length(String) to length(CharSequence)

capitalize

public static String capitalize(String str)

Capitalizes a String changing the first character to title case as per Character.toTitleCase(int). No other characters are changed.

A null input String returns null.

 StringUtils.capitalize(null)  = null
 StringUtils.capitalize("")    = ""
 StringUtils.capitalize("cat") = "Cat"
 StringUtils.capitalize("cAt") = "CAt"
 StringUtils.capitalize("'cat'") = "'cat'"
 

Parameters:

str - the String to capitalize, may be null

Returns:

the capitalized String, null if null String input

Since:

2.0

isAlpha

public static boolean isAlpha(String cs)

Checks if the CharSequence contains only Unicode letters.

null will return false. An empty CharSequence (length()=0) will return false.

 StringUtils.isAlpha(null)   = false
 StringUtils.isAlpha("")     = false
 StringUtils.isAlpha("  ")   = false
 StringUtils.isAlpha("abc")  = true
 StringUtils.isAlpha("ab2c") = false
 StringUtils.isAlpha("ab-c") = false
 

Parameters:

cs - the CharSequence to check, may be null

Returns:

true if only contains letters, and is non-null

Since:

3.0 Changed signature from isAlpha(String) to isAlpha(CharSequence), 3.0 Changed "" to return false and not true

isAlphanumeric

public static boolean isAlphanumeric(String cs)

Checks if the CharSequence contains only Unicode letters or digits.

null will return false. An empty CharSequence (length()=0) will return false.

 StringUtils.isAlphanumeric(null)   = false
 StringUtils.isAlphanumeric("")     = false
 StringUtils.isAlphanumeric("  ")   = false
 StringUtils.isAlphanumeric("abc")  = true
 StringUtils.isAlphanumeric("ab c") = false
 StringUtils.isAlphanumeric("ab2c") = true
 StringUtils.isAlphanumeric("ab-c") = false
 

Parameters:

cs - the CharSequence to check, may be null

Returns:

true if only contains letters or digits, and is non-null

Since:

3.0 Changed signature from isAlphanumeric(String) to isAlphanumeric(CharSequence), 3.0 Changed "" to return false and not true

isNumeric

public static boolean isNumeric(String cs)

Checks if the CharSequence contains only Unicode digits. A decimal point is not a Unicode digit and returns false.

null will return false. An empty CharSequence (length()=0) will return false.

Note that the method does not allow for a leading sign, either positive or negative. Also, if a String passes the numeric test, it may still generate a NumberFormatException when parsed by Integer.parseInt or Long.parseLong, e.g. if the value is outside the range for int or long respectively.

 StringUtils.isNumeric(null)   = false
 StringUtils.isNumeric("")     = false
 StringUtils.isNumeric("  ")   = false
 StringUtils.isNumeric("123")  = true
 StringUtils.isNumeric("१२३")  = true
 StringUtils.isNumeric("12 3") = false
 StringUtils.isNumeric("ab2c") = false
 StringUtils.isNumeric("12-3") = false
 StringUtils.isNumeric("12.3") = false
 StringUtils.isNumeric("-123") = false
 StringUtils.isNumeric("+123") = false
 

Parameters:

cs - the CharSequence to check, may be null

Returns:

true if only contains digits, and is non-null

Since:

3.0 Changed signature from isNumeric(String) to isNumeric(CharSequence), 3.0 Changed "" to return false and not true

isAllLowerCase

public static boolean isAllLowerCase(String cs)

Checks if the CharSequence contains only lowercase characters.

null will return false. An empty CharSequence (length()=0) will return false.

 StringUtils.isAllLowerCase(null)   = false
 StringUtils.isAllLowerCase("")     = false
 StringUtils.isAllLowerCase("  ")   = false
 StringUtils.isAllLowerCase("abc")  = true
 StringUtils.isAllLowerCase("abC")  = false
 StringUtils.isAllLowerCase("ab c") = false
 StringUtils.isAllLowerCase("ab1c") = false
 StringUtils.isAllLowerCase("ab/c") = false
 

Parameters:

cs - the CharSequence to check, may be null

Returns:

true if only contains lowercase characters, and is non-null

Since:

2.5, 3.0 Changed signature from isAllLowerCase(String) to isAllLowerCase(CharSequence)

isAllUpperCase

public static boolean isAllUpperCase(String cs)

Checks if the CharSequence contains only uppercase characters.

null will return false. An empty String (length()=0) will return false.

 StringUtils.isAllUpperCase(null)   = false
 StringUtils.isAllUpperCase("")     = false
 StringUtils.isAllUpperCase("  ")   = false
 StringUtils.isAllUpperCase("ABC")  = true
 StringUtils.isAllUpperCase("aBC")  = false
 StringUtils.isAllUpperCase("A C")  = false
 StringUtils.isAllUpperCase("A1C")  = false
 StringUtils.isAllUpperCase("A/C")  = false
 

Parameters:

cs - the CharSequence to check, may be null

Returns:

true if only contains uppercase characters, and is non-null

Since:

2.5, 3.0 Changed signature from isAllUpperCase(String) to isAllUpperCase(CharSequence)

removeZeroDecimal

public static String removeZeroDecimal(String str)

Removes all trailing zero decimals from the given String, assuming all decimals are zero and any zero decimals actually exist.

A null input String returns null.

Parameters:

str - the String to handle, may be null

Returns:

string without trailing zero decimals

abbreviate

public static String abbreviate(String str,
 String abbrevMarker,
 int maxWidth)

Abbreviates a String using ellipses. This will turn "Now is the time for all good men" into "Now is the time for..."

Specifically:

• If the number of characters in str is less than or equal to maxWidth, return str.
• Else abbreviate it to (substring(str, 0, max-3) + "...").
• If maxWidth is less than 4, throw an IllegalArgumentException.
• In no case will it return a String of length greater than maxWidth.

 StringUtils.abbreviate(null, *)      = null
 StringUtils.abbreviate("", 4)        = ""
 StringUtils.abbreviate("abcdefg", 6) = "abc..."
 StringUtils.abbreviate("abcdefg", 7) = "abcdefg"
 StringUtils.abbreviate("abcdefg", 8) = "abcdefg"
 StringUtils.abbreviate("abcdefg", 4) = "a..."
 StringUtils.abbreviate("abcdefg", 3) = IllegalArgumentException
 

Parameters:

str - the String to check, may be null

abbrevMarker - the String indicate abbreviation

maxWidth - maximum length of result String, must be at least 4

Returns:

abbreviated String, null if null String input

Throws:

IllegalArgumentException - if the width is too small

Since:

2.0