Java 数组和字符串的转换--不能通过toString方法

java数组->字符串

       java中所有的类，不管是java库里面的类，或者是你自己创建的类，全部是从object这个类继承的。object里有一个方法就是toString()，那么所有的类创建的时候，都有一个toString的方法。这个方法是干什么的呢？

首先我们得了解，java输出用的函数print();是不接受对象直接输出的，只接受字符串或者数字之类的输出。

Object类中的toString()方法的源代码如下：

    /**
     * Returns a string representation of the object. In general, the
     * {@code toString} method returns a string that
     * "textually represents" this object. The result should
     * be a concise but informative representation that is easy for a
     * person to read.
     * It is recommended that all subclasses override this method.
     * <p>
     * The {@code toString} method for class {@code Object}
     * returns a string consisting of the name of the class of which the
     * object is an instance, the at-sign character `{@code @}', and
     * the unsigned hexadecimal representation of the hash code of the
     * object. In other words, this method returns a string equal to the
     * value of:
     * <blockquote>
     * <pre>
     * getClass().getName() + '@' + Integer.toHexString(hashCode())
     * </pre></blockquote>
     *
     * @return  a string representation of the object.
     */
    public String toString() {
        return getClass().getName() + "@" + Integer.toHexString(hashCode());
    }

char[] data = {'a', 'b', 'c'};
System.out.println(data.toString());  //输出结果为[C@79fc7299

输出会去调用object类里面的toString 方法，根据源码可知，输出结果为[类型@哈希值]。

而数组类中并没有对此方法重写(override)，仅仅是重载(overload)为类的静态方法（参见java.util.Arrays）。

所以，数组直接使用toString()，会去调用object类里面的toString方法，结果是[类型@哈希值]。

数组转字符串可以使用Arrays类中的toString方法Arrays.toString(data)。附上Arrays类的toString方法源码。但是由源码可知，这种方法的toString()是带格式的，也就是说输出的是[a, b, c]。

 /**
     * Returns a string representation of the contents of the specified array.
     * The string representation consists of a list of the array's elements,
     * enclosed in square brackets (<tt>"[]"</tt>).  Adjacent elements are
     * separated by the characters <tt>", "</tt> (a comma followed by a
     * space).  Elements are converted to strings as by
     * <tt>String.valueOf(char)</tt>.  Returns <tt>"null"</tt> if <tt>a</tt>
     * is <tt>null</tt>.
     *
     * @param a the array whose string representation to return
     * @return a string representation of <tt>a</tt>
     * @since 1.5
     */
    public static String toString(char[] a) {
        if (a == null)
            return "null";
        int iMax = a.length - 1;
        if (iMax == -1)
            return "[]";

        StringBuilder b = new StringBuilder();
        b.append('[');
        for (int i = 0; ; i++) {
            b.append(a[i]);
            if (i == iMax)
                return b.append(']').toString();
            b.append(", ");
        }
    }

如果仅仅想输出abc则需用以下两种方法：

　　方法1：直接在构造String时转换。

        char[] data = {'a', 'b', 'c'};
	String str = new String(data);

　　方法2：调用String类的方法转换。

        String.valueOf(data)

String类valueOf方法的源码如下，由源码可知，valueOf实际也是new String对象，和方法1一样。

/**
     * Returns the string representation of the <code>char</code> array
     * argument. The contents of the character array are copied; subsequent
     * modification of the character array does not affect the newly
     * created string.
     *
     * @param   data   a <code>char</code> array.
     * @return  a newly allocated string representing the same sequence of
     *          characters contained in the character array argument.
     */
    public static String valueOf(char data[]) {
        return new String(data);
    }

java字符串->数组

   如果是 “字符串数组” 转 “字符串”，只能通过循环，没有其它方法 
    String str = "123abc";
    char[] arr = str.toCharArray();　　//char数组
    for(int i =0;i<arr.length;i++)
        System.out.println(arr[i]);    //1 2 3 a b c
    String str = "123abc";    
    for(int i=0;i<str.length();i++)
        System.out.print(str.charAt(i));//也可以通过charAt（）来读取输出

   String[] str = {"abc", "bcd", "def"};
   StringBuffer sb = new StringBuffer();
   for(int i = 0; i < str.length; i++){
         sb.append(str[i]);
}

参考 http://www.cnblogs.com/ningvsban/p/3955483.html
考 http://www.cnblogs.com/ningvsban/p/3955483.html