よくある対象_Integerの直接の賦課の面接試験問題

package cn.itcast_06;

/*
 *       
 * 
 *   :Integer       ,   -127 128  ,            。
 */
public class IntegerDemo {
	public static void main(String[] args) {
		Integer i1 = new Integer(127);//false,    new       
		Integer i2 = new Integer(127);
		System.out.println(i1 == i2);
		System.out.println(i1.equals(i2));
		System.out.println("-----------");

		Integer i3 = new Integer(128);//false,    new       
		Integer i4 = new Integer(128);
		System.out.println(i3 == i4);
		System.out.println(i3.equals(i4));
		System.out.println("-----------");

		Integer i5 = 128;
		Integer i6 = 128;
		System.out.println(i5 == i6);//false,      new       
		System.out.println(i5.equals(i6));
		System.out.println("-----------");

		Integer i7 = 127;
		Integer i8 = 127;
		System.out.println(i7 == i8);//     ,  true,  false
		System.out.println(i7.equals(i8));
		System.out.println("-----------");
		
		Integer i9 = 126;
		Integer i10 = 126;
		System.out.println(i9 == i10);
		System.out.println(i9.equals(i10));
		System.out.println("-----------");
		//       ,      ,  -128 127     ,         ,          ,          
		// Integer ii = Integer.valueOf(127);

		// public static Integer valueOf(int i) {
		// final int offset = 128;
		// if (i >= -128 && i <= 127) { //127>=-128 && 127<=127, 126>=128 && 126<=127
		// return IntegerCache.cache[i + offset];//127+128=255, 126+128=254
		// }
		// return new Integer(i);
		// }

		// private static class IntegerCache {
		// private IntegerCache(){}
		//
		// static final Integer cache[] = new Integer[-(-128) + 127 + 1];//0   255, 0   254
		//
		// static {
		// for(int i = 0; i < cache.length; i++)//0
		// cache[i] = new Integer(i - 128);//255 = new Integer(i-128), 254 = new Integer(i - 128)
		// }
		// }

	}
}