1 public static void main(string[] args) { 2 int i1 = 128; 3 integer i2 = 128; 4 integer i3 = new integer(128); 5 system.out.println(i1 == i2);//true 6 system.out.println(i1 == i3);//true 7 system.out.println("**************************************"); 8 integer i4 = 127; 9 integer i5 = 127; 10 integer i6 = 128; 11 integer i7 = 128; 12 system.out.println(i4 == i5);//true 13 system.out.println(i6 == i7);//false 14 system.out.println("**************************************"); 15 integer i8 = new integer(127); 16 integer i9 = new integer(127); 17 system.out.println(i8 == i9);//false 18 system.out.println(i8.equals(i9));//true 19 system.out.println(i4 == i8);//false 20 /* output: 21 true 22 true 23 ************************************** 24 true 25 false 26 ************************************** 27 false 28 true 29 false 30 */ 31 }
/** * returns an {@code integer} instance representing the specified * {@code int} value. if a new {@code integer} instance is not * required, this method should generally be used in preference to * the constructor {@link #integer(int)}, as this method is likely * to yield significantly better space and time performance by * caching frequently requested values. * * this method will always cache values in the range -128 to 127, * inclusive, and may cache other values outside of this range. * * @param i an {@code int} value. * @return an {@code integer} instance representing {@code i}. * @since 1.5 */ public static integer valueof(int i) { if (i >= integercache.low && i <= integercache.high) return integercache.cache[i + (-integercache.low)]; return new integer(i); }
看一下源码大家就会明白,对于-128到127之间的数,会进行缓存,integer i6 = 127时,会将127进行缓存,下次再写integer i7 = 127时,就会直接从缓存中取,就不会new了。
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