The cache for integer

How to get an integer instance based on the integer class:

Integer instance=new integer (int value);

Integer instance=integer.valueof (int value);

The first approach will certainly produce a new instance each time, but the second way is not:

1  Public Static voidMain (String[]args) {2Integer i1=integer.valueof (127);3Integer i2=integer.valueof (127);4System.out.println (i1==i2);5         6Integer i3=integer.valueof (128);7Integer i4=integer.valueof (128);8System.out.println (i3==I4);9         TenInteger i5=integer.valueof (-128); OneInteger i6=integer.valueof (-128); ASystem.out.println (i5==I6); -          -Integer i7=integer.valueof (-129); theInteger i8=integer.valueof (-129); -System.out.println (i7==i8); -}

Truefalsetruefalse

This result is caused because the integer class internally caches an instance of the range [-128,127] of the value of 128 to 127.

Similar to the following code:

1  Public classTest {2      Public Static voidMain (String[]args) {3Myinteger i1=myinteger.valueof (10);4Myinteger i2=myinteger.valueof (10);5System.out.println (i1==i2);6         7Myinteger i3=myinteger.valueof (11);8Myinteger i4=myinteger.valueof (11);9System.out.println (i3==I4);Ten     } One } A  - classMyinteger { -     Private Final intvalue; the      PublicMyinteger (intvalue) { -          This. value=value; -     } -      Public StaticMyinteger ValueOf (inti) { +myinteger[]caches=MyInteger.MyIntegerCache.caches; -         if(i>=1&&i<=10) { +             returnCaches[i-1]; A         } at         return NewMyinteger (i); -     } -      -     Static classMyintegercache { -         Staticmyinteger[]caches=NewMyinteger[10]; -         Static { in              for(inti=0;i<10;i++) { -caches[i]=NewMyinteger (i+1); to             } +         } -     } the}

The cache for integer