String转char[],char转String

Posted 2021-07-05 zhangjin1120

• String 转 char[]，例如：把一个单词转为一个字符数组。

  char[] letter = content.toCharArray();

toCharArray()的android 源码，是被改动过的。

在open jdk8 String.java中,toCharArray()的源码如下，

   /**
     * Converts this string to a new character array.
     *
     * @return  a newly allocated character array whose length is the length
     *          of this string and whose contents are initialized to contain
     *          the character sequence represented by this string.
     */
    public char[] toCharArray() {
        // Cannot use Arrays.copyOf because of class initialization order issues
        char result[] = new char[value.length];
        System.arraycopy(value, 0, result, 0, value.length);
        return result;
    }

可以看到，toCharArray()采用的是System.copy(),而System.copy()本身是一个native方法，有时间再往下追究。

    public static native void arraycopy(Object src,  int  srcPos,
                                        Object dest, int destPos,
                                        int length);

• char转String，例如：java Bean类中，经常有String成员变量，单个字符char，需要转为String类。

String str = String.valueOf(c);