String和常量池值的變化

public static void main(String[] args) {
        Integer i1 = new Integer(1);
        Integer i2 = new Integer(1);
        // i1,i2分別位於堆中不同的記憶體空間
        System.out.println("i1 == i2:" + (i1 == i2));// 輸出false

        String s1 = "china";

        String s2 = "china";

        String ss1 = new String("china");

        String ss2 = new String("china");

        System.out.println("s1 == s2:" + (s1 == s2));
        System.out.println("ss1 == ss2" + (ss1 == ss2));
        System.out.println("s1 == ss2" + (s1 == ss2));

        // 利用Java反射機制改變string的值
        Field f = null;
        Field f1 = null;
        try {
            f = s1.getClass().getDeclaredField("value");
            f1 = ss1.getClass().getDeclaredField("value");
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
        f.setAccessible(true);
        f1.setAccessible(true);
        try {
            f.set(s1, new char[] { 'c', 'h', 'i', 'n', 'b' });
            f1.set(ss1, new char[] { 'c', 'h', 'i', 'n', 'b' });
        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println("改變後的s1的值：" + s1);
        System.out.println("s2的值是：" + s2);
        System.out.println("ss1的值是：" + ss1);
        System.out.println("s1 == s2:" + (s1 == s2));
        System.out.println("ss1 == ss2" + (ss1 == ss2));
        System.out.println("s1 == ss2" + (s1 == ss2));
        System.out.println("============分割線==================");
        System.out.println("改變後的ss1的值：" + ss1);
        System.out.println("ss2的值是：" + ss2);

    }

列印的結果：

i1 == i2:false
s1 == s2:true
ss1 == ss2false
s1 == ss2false
改變後的s1的值：chinb
s2的值是：chinb
ss1的值是：chinb
s1 == s2:true
ss1 == ss2false
s1 == ss2false
============分割線==================
改變後的ss1的值：chinb
ss2的值是：china