Efficiency issues in objective java

Source: Internet
Author: User

Package com. liuc; public class AutoPackage {public static void main (String [] args) {long start = System. currentTimeMillis (); long sum = 0L; for (int I = 0; I <Integer. MAX_VALUE; I ++) {sum + = I;} long end = System. currentTimeMillis (); System. out. println (end-start)/1000 );}}

Running time: 19 S

And the following program

Package com. liuc; public class AutoPackage {public static void main (String [] args) {long start = System. currentTimeMillis (); Long sum = 0L; for (int I = 0; I <Integer. MAX_VALUE; I ++) {sum + = I;} long end = System. currentTimeMillis (); System. out. println (end-start)/1000 );}}

Running time: 19 S

The efficiency gap is so large that we only perform an automatic packing operation each time. Therefore, when performing a large number of operations, pay attention to code-level optimization.




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