と言う事は

    public static void main(String[] args) {
    	System.out.println(Boolean.valueOf("true"));
    	System.out.println(Boolean.getBoolean("true"));

    	System.setProperty("true", "true");
    	System.out.println(Boolean.valueOf("true"));
    	System.out.println(Boolean.getBoolean("true"));

    	System.setProperty("true", "false");
    	System.out.println(Boolean.valueOf("true"));
    	System.out.println(Boolean.getBoolean("true"));
    }

の結果は

true
false
true
true
true
false

になるのねん♪