package com.ctrip.apollo.core.utils;

 import java.util.Collection;

 import java.util.Iterator;

 public class StringUtils {

   public static final String EMPTY = "";

   /**

    * <p>

    * Checks if a String is empty ("") or null.

    * </p>

    *

    * <pre>

    * StringUtils.isEmpty(null)      = true

    * StringUtils.isEmpty("")        = true

    * StringUtils.isEmpty(" ")       = false

    * StringUtils.isEmpty("bob")     = false

    * StringUtils.isEmpty("  bob  ") = false

    * </pre>

    *

    * <p>

    * NOTE: This method changed in Lang version 2.0. It no longer trims the String. That functionality is available in isBlank().

    * </p>

    *

    * @param str the String to check, may be null

    * @return <code>true</code> if the String is empty or null

    */

   public static boolean isEmpty(String str) {

     return str == null || str.length() == 0;

   }

   public static boolean isContainEmpty(String... args){

     if (args == null){

       return false;

     }

     for (String arg: args){

       if (arg == null || "".equals(arg)){

         return true;

       }

     }

     return false;

   }

   /**

    * <p>

    * Checks if a String is whitespace, empty ("") or null.

    * </p>

    *

    * <pre>

    * StringUtils.isBlank(null)      = true

    * StringUtils.isBlank("")        = true

    * StringUtils.isBlank(" ")       = true

    * StringUtils.isBlank("bob")     = false

    * StringUtils.isBlank("  bob  ") = false

    * </pre>

    *

    * @param str the String to check, may be null

    * @return <code>true</code> if the String is null, empty or whitespace

    */

   public static boolean isBlank(String str) {

     int strLen;

     if (str == null || (strLen = str.length()) == 0) {

       return true;

     }

     for (int i = 0; i < strLen; i++) {

       if (Character.isWhitespace(str.charAt(i)) == false) {

         return false;

       }

     }

     return true;

   }

   /**

    * <p>

    * Removes control characters (char &lt;= 32) from both ends of this String returning <code>null</code> if the String is empty

    * ("") after the trim or if it is <code>null</code>.

    *

    * <p>

    * The String is trimmed using {@link String#trim()}. Trim removes start and end characters <= 32. To strip whitespace use

    * {@link #stripToNull(String)}.

    * </p>

    *

    * <pre>

    * StringUtils.trimToNull(null)          = null

    * StringUtils.trimToNull("")            = null

    * StringUtils.trimToNull("     ")       = null

    * StringUtils.trimToNull("abc")         = "abc"

    * StringUtils.trimToNull("    abc    ") = "abc"

    * </pre>

    *

    * @param str the String to be trimmed, may be null

    * @return the trimmed String, <code>null</code> if only chars &lt;= 32, empty or null String input

    * @since 2.0

    */

   public static String trimToNull(String str) {

     String ts = trim(str);

     return isEmpty(ts) ? null : ts;

   }

   /**

    * <p>

    * Removes control characters (char <= 32) from both ends of this String returning an empty String ("") if the String is empty

    * ("") after the trim or if it is <code>null</code>.

    *

    * <p>

    * The String is trimmed using {@link String#trim()}. Trim removes start and end characters <= 32. To strip whitespace use

    * {@link #stripToEmpty(String)}.

    * </p>

    *

    * <pre>

    * StringUtils.trimToEmpty(null)          = ""

    * StringUtils.trimToEmpty("")            = ""

    * StringUtils.trimToEmpty("     ")       = ""

    * StringUtils.trimToEmpty("abc")         = "abc"

    * StringUtils.trimToEmpty("    abc    ") = "abc"

    * </pre>

    *

    * @param str the String to be trimmed, may be null

    * @return the trimmed String, or an empty String if <code>null</code> input

    * @since 2.0

    */

   public static String trimToEmpty(String str) {

     return str == null ? EMPTY : str.trim();

   }

   /**

    * <p>

    * Removes control characters (char &lt;= 32) from both ends of this String, handling <code>null</code> by returning

    * <code>null</code>.

    * </p>

    *

    * <p>

    * The String is trimmed using {@link String#trim()}. Trim removes start and end characters <= 32. To strip whitespace use

    * {@link #strip(String)}.

    * </p>

    *

    * <p>

    * To trim your choice of characters, use the {@link #strip(String, String)} methods.

    * </p>

    *

    * <pre>

    * StringUtils.trim(null)          = null

    * StringUtils.trim("")            = ""

    * StringUtils.trim("     ")       = ""

    * StringUtils.trim("abc")         = "abc"

    * StringUtils.trim("    abc    ") = "abc"

    * </pre>

    *

    * @param str the String to be trimmed, may be null

    * @return the trimmed string, <code>null</code> if null String input

    */

   public static String trim(String str) {

     return str == null ? null : str.trim();

   }

   /**

    * <p>

    * Compares two Strings, returning <code>true</code> if they are equal.

    * </p>

    *

    * <p>

    * <code>null</code>s are handled without exceptions. Two <code>null</code> references are considered to be equal. The comparison

    * is case sensitive.

    * </p>

    *

    * <pre>

    * StringUtils.equals(null, null)   = true

    * StringUtils.equals(null, "abc")  = false

    * StringUtils.equals("abc", null)  = false

    * StringUtils.equals("abc", "abc") = true

    * StringUtils.equals("abc", "ABC") = false

    * </pre>

    *

    * @param str1 the first String, may be null

    * @param str2 the second String, may be null

    * @return <code>true</code> if the Strings are equal, case sensitive, or both <code>null</code>

    * @see java.lang.String#equals(Object)

    */

   public static boolean equals(String str1, String str2) {

     return str1 == null ? str2 == null : str1.equals(str2);

   }

   /**

    * <p>

    * Compares two Strings, returning <code>true</code> if they are equal ignoring the case.

    * </p>

    *

    * <p>

    * <code>null</code>s are handled without exceptions. Two <code>null</code> references are considered equal. Comparison is case

    * insensitive.

    * </p>

    *

    * <pre>

    * StringUtils.equalsIgnoreCase(null, null)   = true

    * StringUtils.equalsIgnoreCase(null, "abc")  = false

    * StringUtils.equalsIgnoreCase("abc", null)  = false

    * StringUtils.equalsIgnoreCase("abc", "abc") = true

    * StringUtils.equalsIgnoreCase("abc", "ABC") = true

    * </pre>

    *

    * @param str1 the first String, may be null

    * @param str2 the second String, may be null

    * @return <code>true</code> if the Strings are equal, case insensitive, or both <code>null</code>

    * @see java.lang.String#equalsIgnoreCase(String)

    */

   public static boolean equalsIgnoreCase(String str1, String str2) {

     return str1 == null ? str2 == null : str1.equalsIgnoreCase(str2);

   }

   /**

    * <p>

    * Check if a String starts with a specified prefix.

    * </p>

    *

    * <p>

    * <code>null</code>s are handled without exceptions. Two <code>null</code> references are considered to be equal. The comparison

    * is case sensitive.

    * </p>

    *

    * <pre>

    * StringUtils.startsWith(null, null)      = true

    * StringUtils.startsWith(null, "abc")     = false

    * StringUtils.startsWith("abcdef", null)  = false

    * StringUtils.startsWith("abcdef", "abc") = true

    * StringUtils.startsWith("ABCDEF", "abc") = false

    * </pre>

    *

    * @param str    the String to check, may be null

    * @param prefix the prefix to find, may be null

    * @return <code>true</code> if the String starts with the prefix, case sensitive, or both <code>null</code>

    * @see java.lang.String#startsWith(String)

    * @since 2.4

    */

   public static boolean startsWith(String str, String prefix) {

     return startsWith(str, prefix, false);

   }

   /**

    * <p>

    * Check if a String starts with a specified prefix (optionally case insensitive).

    * </p>

    *

    * @param str        the String to check, may be null

    * @param prefix     the prefix to find, may be null

    * @param ignoreCase inidicates whether the compare should ignore case (case insensitive) or not.

    * @return <code>true</code> if the String starts with the prefix or both <code>null</code>

    * @see java.lang.String#startsWith(String)

    */

   private static boolean startsWith(String str, String prefix, boolean ignoreCase) {

     if (str == null || prefix == null) {

       return str == null && prefix == null;

     }

     if (prefix.length() > str.length()) {

       return false;

     }

     return str.regionMatches(ignoreCase, 0, prefix, 0, prefix.length());

   }

   /**

    * <p>

    * Case insensitive check if a String starts with a specified prefix.

    * </p>

    *

    * <p>

    * <code>null</code>s are handled without exceptions. Two <code>null</code> references are considered to be equal. The comparison

    * is case insensitive.

    * </p>

    *

    * <pre>

    * StringUtils.startsWithIgnoreCase(null, null)      = true

    * StringUtils.startsWithIgnoreCase(null, "abc")     = false

    * StringUtils.startsWithIgnoreCase("abcdef", null)  = false

    * StringUtils.startsWithIgnoreCase("abcdef", "abc") = true

    * StringUtils.startsWithIgnoreCase("ABCDEF", "abc") = true

    * </pre>

    *

    * @param str    the String to check, may be null

    * @param prefix the prefix to find, may be null

    * @return <code>true</code> if the String starts with the prefix, case insensitive, or both <code>null</code>

    * @see java.lang.String#startsWith(String)

    * @since 2.4

    */

   public static boolean startsWithIgnoreCase(String str, String prefix) {

     return startsWith(str, prefix, true);

   }

   /**

    * <p>

    * Checks if the String contains only unicode digits. A decimal point is not a unicode digit and returns false.

    * </p>

    *

    * <p>

    * <code>null</code> will return <code>false</code>. An empty String (length()=0) will return <code>true</code>.

    * </p>

    *

    * <pre>

    * StringUtils.isNumeric(null)   = false

    * StringUtils.isNumeric("")     = true

    * StringUtils.isNumeric("  ")   = false

    * StringUtils.isNumeric("123")  = true

    * StringUtils.isNumeric("12 3") = false

    * StringUtils.isNumeric("ab2c") = false

    * StringUtils.isNumeric("12-3") = false

    * StringUtils.isNumeric("12.3") = false

    * </pre>

    *

    * @param str the String to check, may be null

    * @return <code>true</code> if only contains digits, and is non-null

    */

   public static boolean isNumeric(String str) {

     if (str == null) {

       return false;

     }

     int sz = str.length();

     for (int i = 0; i < sz; i++) {

       if (Character.isDigit(str.charAt(i)) == false) {

         return false;

       }

     }

     return true;

   }

   public static interface StringFormatter<T> {

     String format(T obj);

   }

   public static <T> String join(Collection<T> collection, String separator) {

     return join(collection, separator, new StringFormatter<T>() {

       @Override

       public String format(T obj) {

         return obj.toString();

       }

     });

   }

   public static <T> String join(Collection<T> collection, String separator,

                                 StringFormatter<T> formatter) {

     Iterator<T> iterator = collection.iterator();

     // handle null, zero and one elements before building a buffer

     if (iterator == null) {

       return null;

     }

     if (!iterator.hasNext()) {

       return EMPTY;

     }

     T first = iterator.next();

     if (!iterator.hasNext()) {

       return first == null ? "" : formatter.format(first);

     }

     // two or more elements

     StringBuilder buf = new StringBuilder(256); // Java default is 16, probably too small

     if (first != null) {

       buf.append(formatter.format(first));

     }

     while (iterator.hasNext()) {

       buf.append(separator);

       T obj = iterator.next();

       if (obj != null) {

         buf.append(formatter.format(obj));

       }

     }

     return buf.toString();

   }

 }