Integer.valueOf与Integer.parseInt的小疑惑

参考博客：

http://www.importnew.com/9162.html

测试代码如下：

public class Main {

    /**
     * 备注：结果跟你的JDK版本有关系：
     *
     * 我的是java version "1.6.0_16"
     *
     *这是JDK中的Integer.java中valueOf的源代码：
      public static Integer valueOf(String s) throws NumberFormatException {
        return Integer.valueOf(parseInt(s, 10));
      }

      public static Integer valueOf(int i) {
        if(i >= -128 && i <= IntegerCache.high)
            return IntegerCache.cache[i + 128];
        else
            return new Integer(i);
     }

     public static int parseInt(String s) throws NumberFormatException {
        return parseInt(s,10);
     }

        public static int parseInt(String s, int radix)
        throws NumberFormatException
    {
        if (s == null) {
            throw new NumberFormatException("null");
        }

    if (radix < Character.MIN_RADIX) {
        throw new NumberFormatException("radix " + radix +
                        " less than Character.MIN_RADIX");
    }

    if (radix > Character.MAX_RADIX) {
        throw new NumberFormatException("radix " + radix +
                        " greater than Character.MAX_RADIX");
    }

    int result = 0;
    boolean negative = false;
    int i = 0, max = s.length();
    int limit;
    int multmin;
    int digit;

    if (max > 0) {
        if (s.charAt(0) == '-') {
        negative = true;
        limit = Integer.MIN_VALUE;
        i++;
        } else {
        limit = -Integer.MAX_VALUE;
        }
        multmin = limit / radix;
        if (i < max) {
        digit = Character.digit(s.charAt(i++),radix);
        if (digit < 0) {
            throw NumberFormatException.forInputString(s);
        } else {
            result = -digit;
        }
        }
        while (i < max) {
        // Accumulating negatively avoids surprises near MAX_VALUE
        digit = Character.digit(s.charAt(i++),radix);
        if (digit < 0) {
            throw NumberFormatException.forInputString(s);
        }
        if (result < multmin) {
            throw NumberFormatException.forInputString(s);
        }
        result *= radix;
        if (result < limit + digit) {
            throw NumberFormatException.forInputString(s);
        }
        result -= digit;
        }
    } else {
        throw NumberFormatException.forInputString(s);
    }
    if (negative) {
        if (i > 1) {
        return result;
        } else {
        throw NumberFormatException.forInputString(s);
        }
    } else {
        return -result;
    }
    }
     * @param args
     */
    public static void main(String[] args) {

        System.out.println(Integer.valueOf(127) == Integer.valueOf(127));
        System.out.println(Integer.valueOf("127") == Integer.valueOf(127));
        System.out.println(Integer.valueOf("127") == Integer.valueOf("127"));

        System.out.println(Integer.parseInt("127") == Integer.parseInt("127"));

        System.out.println(Integer.valueOf(127) == Integer.parseInt("127"));
        System.out.println(Integer.valueOf("127") == Integer.parseInt("127"));

        System.out.println(Integer.valueOf(128) == Integer.valueOf(128));
        System.out.println(Integer.valueOf("128") == Integer.valueOf(128));
        System.out.println(Integer.valueOf("128") == Integer.valueOf("128"));

        System.out.println(Integer.parseInt("128") == Integer.parseInt("128"));

        System.out.println(Integer.valueOf(128) == Integer.parseInt("128"));
        System.out.println(Integer.valueOf("128") == Integer.parseInt("128"));

    }
    /**
    true
    true
    true
    true
    true
    true
    false
    false
    false
    true
    true
    true
    */

}