JavaSE_坚持读源码_String对象_Java1.7

 　　/**
      * Compares this string to the specified object.  The result is {@code
      * true} if and only if the argument is not {@code null} and is a {@code
      * String} object that represents the same sequence of characters as this
      * object.
      *
      * @param  anObject
      *         The object to compare this {@code String} against
      *
      * @return  {@code true} if the given object represents a {@code String}
      *          equivalent to this string, {@code false} otherwise
      *
      * @see  #compareTo(String)
      * @see  #equalsIgnoreCase(String)
      */
     public boolean equals(Object anObject) {
         if (this == anObject) {
             return true;
         }
         if (anObject instanceof String) {
             String anotherString = (String) anObject;
             int n = value.length;
             if (n == anotherString.value.length) {
                 char v1[] = value;
                 char v2[] = anotherString.value;
                 int i = 0;
                 while (n-- != 0) {
                     if (v1[i] != v2[i])
                             return false;
                     i++;
                 }
                 return true;
             }
         }
         return false;
     }

String对象将Object的equals方法重写了，当且仅当equals的参数：1.不是null，2.是个与比较对象的字符序列相同的String对象；返回true

由于重写了equals方法，所以需要把hashCode方法重写

 　　/**
      * Returns a hash code for this string. The hash code for a
      * <code>String</code> object is computed as
      * <blockquote><pre>
      * s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
      * </pre></blockquote>
      * using <code>int</code> arithmetic, where <code>s[i]</code> is the
      * <i>i</i>th character of the string, <code>n</code> is the length of
      * the string, and <code>^</code> indicates exponentiation.
      * (The hash value of the empty string is zero.)
      *
      * @return  a hash code value for this object.
      */
     public int hashCode() {
         int h = hash;
         if (h == 0 && value.length > 0) {
             char val[] = value;

             for (int i = 0; i < value.length; i++) {
                 h = 31 * h + val[i];
             }
             hash = h;
         }
         return h;
     }