首先是包装类型

		Long sum = Long.valueOf(0);
		long t1 = System.currentTimeMillis();
		for (Long i = Long.valueOf(0); i < Integer.MAX_VALUE/2; i++) {
			sum += i;
		}
		t1 = System.currentTimeMillis() - t1;
		System.out.println("packaging took "+ t1 +" sum = "+ sum);

耗时：12759ms

装箱拆箱

		Long sum = 0L;
		
		long t0 = System.currentTimeMillis();
		for (long i = 0; i < Integer.MAX_VALUE/2; i++) {
			sum += i;
		}
		t0 = System.currentTimeMillis() - t0;
		System.out.println("Unboxing Boxing took "+ t0 +" sum = "+ sum);

耗时：6144ms

基本类型

		long s = 0L;
		long t2 = System.currentTimeMillis();
		for (long i = 0L; i < Integer.MAX_VALUE/2; i++) {
			s += i;
		}
		t2 = System.currentTimeMillis() - t2;
		System.out.println("prime took "+ t2 +" sum = "+ s);

耗时：581ms

速度之差立杆见影，基本类型的速度约是包装类型的21倍，装箱拆箱的10倍。

装箱拆箱那段代码是容易写错的地方，一个大小写之差。

优先使用基本类型的论点是有道理的。