com.google.common.base

Class Strings

java.lang.Object

com.google.common.base.Strings

@GwtCompatible
public final class Strings
extends Object

Static utility methods pertaining to String or CharSequence instances.

Since:

3.0

Author:

Kevin Bourrillion

Method Summary

Modifier and Type	Method and Description
static String	commonPrefix(CharSequence a, CharSequence b) Returns the longest string prefix such that a.toString().startsWith(prefix) && b.toString().startsWith(prefix), taking care not to split surrogate pairs.
static String	commonSuffix(CharSequence a, CharSequence b) Returns the longest string suffix such that a.toString().endsWith(suffix) && b.toString().endsWith(suffix), taking care not to split surrogate pairs.
static String	emptyToNull(String string) Returns the given string if it is nonempty; null otherwise.
static boolean	isNullOrEmpty(String string) Returns true if the given string is null or is the empty string.
static String	lenientFormat(String template, Object... args) Returns the given template string with each occurrence of "%s" replaced with the corresponding argument value from args; or, if the placeholder and argument counts do not match, returns a best-effort form of that string.
static String	nullToEmpty(String string) Returns the given string if it is non-null; the empty string otherwise.
static String	padEnd(String string, int minLength, char padChar) Returns a string, of length at least minLength, consisting of string appended with as many copies of padChar as are necessary to reach that length.
static String	padStart(String string, int minLength, char padChar) Returns a string, of length at least minLength, consisting of string prepended with as many copies of padChar as are necessary to reach that length.
static String	repeat(String string, int count) Returns a string consisting of a specific number of concatenated copies of an input string.

Methods inherited from class java.lang.Object

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

Method Detail

nullToEmpty

public static String nullToEmpty(@NullableDecl
                                 String string)

Returns the given string if it is non-null; the empty string otherwise.

Parameters:

string - the string to test and possibly return

Returns:

string itself if it is non-null; "" if it is null

emptyToNull

@NullableDecl
public static String emptyToNull(@NullableDecl
                                               String string)

Returns the given string if it is nonempty; null otherwise.

Parameters:

string - the string to test and possibly return

Returns:

string itself if it is nonempty; null if it is empty or null

isNullOrEmpty

public static boolean isNullOrEmpty(@NullableDecl
                                    String string)

Returns true if the given string is null or is the empty string.

Consider normalizing your string references with nullToEmpty(java.lang.String). If you do, you can use String.isEmpty() instead of this method, and you won't need special null-safe forms of methods like String.toUpperCase(java.util.Locale) either. Or, if you'd like to normalize "in the other direction," converting empty strings to null, you can use emptyToNull(java.lang.String).

Parameters:

string - a string reference to check

Returns:

true if the string is null or is the empty string

padStart

public static String padStart(String string,
                              int minLength,
                              char padChar)

Returns a string, of length at least minLength, consisting of string prepended with as many copies of padChar as are necessary to reach that length. For example,

• padStart("7", 3, '0') returns "007"
• padStart("2010", 3, '0') returns "2010"

See Formatter for a richer set of formatting capabilities.

Parameters:

string - the string which should appear at the end of the result

minLength - the minimum length the resulting string must have. Can be zero or negative, in which case the input string is always returned.

padChar - the character to insert at the beginning of the result until the minimum length is reached

Returns:

the padded string

padEnd

public static String padEnd(String string,
                            int minLength,
                            char padChar)

Returns a string, of length at least minLength, consisting of string appended with as many copies of padChar as are necessary to reach that length. For example,

• padEnd("4.", 5, '0') returns "4.000"
• padEnd("2010", 3, '!') returns "2010"

See Formatter for a richer set of formatting capabilities.

Parameters:

string - the string which should appear at the beginning of the result

minLength - the minimum length the resulting string must have. Can be zero or negative, in which case the input string is always returned.

padChar - the character to append to the end of the result until the minimum length is reached

Returns:

the padded string

repeat

public static String repeat(String string,
                            int count)

Returns a string consisting of a specific number of concatenated copies of an input string. For example, repeat("hey", 3) returns the string "heyheyhey".

Parameters:

string - any non-null string

count - the number of times to repeat it; a nonnegative integer

Returns:

a string containing string repeated count times (the empty string if count is zero)

Throws:

IllegalArgumentException - if count is negative

commonPrefix

public static String commonPrefix(CharSequence a,
                                  CharSequence b)

Returns the longest string prefix such that a.toString().startsWith(prefix) && b.toString().startsWith(prefix), taking care not to split surrogate pairs. If a and b have no common prefix, returns the empty string.

Since:

11.0

commonSuffix

public static String commonSuffix(CharSequence a,
                                  CharSequence b)

Returns the longest string suffix such that a.toString().endsWith(suffix) && b.toString().endsWith(suffix), taking care not to split surrogate pairs. If a and b have no common suffix, returns the empty string.

Since:

11.0

lenientFormat

public static String lenientFormat(@NullableDecl
                                   String template,
                                   @NullableDecl
                                   Object... args)

Returns the given template string with each occurrence of "%s" replaced with the corresponding argument value from args; or, if the placeholder and argument counts do not match, returns a best-effort form of that string. Will not throw an exception under any circumstances (as long as all arguments' toString methods successfully return).

Note: For most string-formatting needs, use String.format(java.lang.String, java.lang.Object...), PrintWriter#format, and related methods. These support the full range of format specifiers, and alert you to usage errors by throwing InvalidFormatException.

In certain cases, such as outputting debugging information or constructing a message to be used for another unchecked exception, an exception during string formatting would serve little purpose except to supplant the real information you were trying to provide. These are the cases this method is made for; it instead generates a best-effort string with all supplied argument values present. This method is also useful in environments such as GWT where String.format is not available. As an example, method implementations of the Preconditions class use this formatter, for both of the reasons just discussed.

Warning: Only the exact two-character placeholder sequence "%s" is recognized.

Parameters:

template - a string containing zero or more "%s" placeholder sequences. null is treated as the four-character string "null".

args - the arguments to be substituted into the message template. The first argument specified is substituted for the first occurrence of "%s" in the template, and so forth. A null argument is converted to the four-character string "null"; non-null values are converted to strings using Object.toString().

Since:

25.1