隔壁帖子看地题目，哪位高手能给解释一下结果

package com.dhcc.yang;public class Test2 {    public static void main(String[] args) {        int k = 100;        Integer int1 = k;        Integer int2 = k;        System.out.println("a." + (int1 == int2));        k = 200;        Integer int3 = k;        Integer int4 = k;        System.out.println("b." + (int3 == int4));        char c = 'A';        Character char1 = c;        Character char2 = c;        System.out.println("c." + (char1 == char2));        c = '国';        Character char3 = c;        Character char4 = c;        System.out.println("d." + (char3 == char4));    }}

public static Integer valueOf(int i) {    final int offset = 128;    if (i >= -128 && i <= 127) { // must cache         return IntegerCache.cache[i + offset];    }        return new Integer(i);    } private static class IntegerCache {    private IntegerCache(){}    static final Integer cache[] = new Integer[-(-128) + 127 + 1];    static {        for(int i = 0; i < cache.length; i++)        cache[i] = new Integer(i - 128);    }    }