com.google.common.base

Class Strings

java.lang.Object

com.google.common.base.Strings

@GwtCompatible
public final class Strings
extends java.lang.Object

Static utility methods pertaining to String or CharSequence instances.

Since:

3.0

Constructor Summary

Constructors

Modifier	Constructor and Description
private	Strings()

Method Summary

Modifier and Type	Method and Description
static java.lang.String	commonPrefix(java.lang.CharSequence a, java.lang.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 java.lang.String	commonSuffix(java.lang.CharSequence a, java.lang.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 java.lang.String	emptyToNull(java.lang.String string) Returns the given string if it is nonempty; null otherwise.
static boolean	isNullOrEmpty(java.lang.String string) Returns true if the given string is null or is the empty string.
static java.lang.String	nullToEmpty(java.lang.String string) Returns the given string if it is non-null; the empty string otherwise.
static java.lang.String	padEnd(java.lang.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 java.lang.String	padStart(java.lang.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 java.lang.String	repeat(java.lang.String string, int count) Returns a string consisting of a specific number of concatenated copies of an input string.
(package private) static boolean	validSurrogatePairAt(java.lang.CharSequence string, int index) True when a valid surrogate pair starts at the given index in the given string.

Methods inherited from class java.lang.Object

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

Constructor Detail

Strings

private Strings()

Method Detail

nullToEmpty

public static java.lang.String nullToEmpty(@Nullable
                                           java.lang.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

@Nullable
public static java.lang.String emptyToNull(@Nullable
                                                     java.lang.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(@Nullable
                                    java.lang.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 java.lang.String padStart(java.lang.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 java.lang.String padEnd(java.lang.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 java.lang.String repeat(java.lang.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:

java.lang.IllegalArgumentException - if count is negative

commonPrefix

public static java.lang.String commonPrefix(java.lang.CharSequence a,
                                            java.lang.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 java.lang.String commonSuffix(java.lang.CharSequence a,
                                            java.lang.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

validSurrogatePairAt

static boolean validSurrogatePairAt(java.lang.CharSequence string,
                                    int index)

True when a valid surrogate pair starts at the given index in the given string. Out-of-range indexes return false.