全面测试嵌套多层For循环的性能和优化方案

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/**
* 全面测试嵌套多层For循环的性能。
*
* @author 老紫竹的家(laozizhu.com)
*
*/
public class TestForLoop {
public static void main(String[] args) {
int small =  1;
int middle = 1000;
int large =  1000000;
// 大循环在外面，小循环在里面，变量每次生成
long t = System.currentTimeMillis();
for (int i = 1; i <= large; i++) {
for (int j = 1; j <= middle; j++) {
for (int k = 1; k <= small; k++) {
}
}
}
System.out.println(System.currentTimeMillis() - t);
// 大循环在外面，小循环在里面，变量统一生成
t = System.currentTimeMillis();
int i, j, k;
for (i = 1; i <= large; i++) {
for (j = 1; j <= middle; j++) {
for (k = 1; k <= small; k++) {
}
}
}
System.out.println(System.currentTimeMillis() - t);
// 小循环在外面，大循环在里面，变量每次生成
t = System.currentTimeMillis();
for (int kk = 1; kk <= small; kk++) {
for (int jj = 1; jj <= middle; jj++) {
for (int ii = 1; ii <= large; ii++) {
}
}
}
System.out.println(System.currentTimeMillis() - t);
// 小循环在外面，大循环在里面，变量统一生成
t = System.currentTimeMillis();
int ii, jj, kk;
for (kk = 1; kk <= small; kk++) {
for (jj = 1; jj <= middle; jj++) {
for (ii = 1; ii <= large; ii++) {
}
}
}
System.out.println(System.currentTimeMillis() - t);
}
}