请问语句a=a*b和a*=b哪个运算速度快?
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请问语句a=a*b和a*=b哪个运算速度快?
另外a=a+1,a+=1,还有a++这三个哪个速度更快呢?
另外a=a+1,a+=1,还有a++这三个哪个速度更快呢?
如果你对java虚拟机,底层原理没有太深的研究,那么可以通过一些技巧来判断.给你个例子public class $ {
public static void main(String... _) {
long size = 10000000000L;
long num = 0;
test1(num, size);
test2(num, size);
test3(num, size);
}
private static void test1(long num, long size) {
long start = System.currentTimeMillis();
for (long i = 0; i < size; i++) {
num = num + 1;
}
System.out.println("a=a+1用时:" + (System.currentTimeMillis() - start));
}
private static void test2(long num, long size) {
long start = System.currentTimeMillis();
for (long i = 0; i < size; i++) {
num += 1;
}
System.out.println("a+=1用时:" + (System.currentTimeMillis() - start));
}
private static void test3(long num, long size) {
long start = System.currentTimeMillis();
for (long i = 0; i < size; i++) {
num++;
}
System.out.println("a++用时:" + (System.currentTimeMillis() - start));
}
}结果a=a+1用时:4551
a+=1用时:4535
a++用时:4512
public static void main(String... _) {
long size = 10000000000L;
long num = 0;
test1(num, size);
test2(num, size);
test3(num, size);
}
private static void test1(long num, long size) {
long start = System.currentTimeMillis();
for (long i = 0; i < size; i++) {
num = num + 1;
}
System.out.println("a=a+1用时:" + (System.currentTimeMillis() - start));
}
private static void test2(long num, long size) {
long start = System.currentTimeMillis();
for (long i = 0; i < size; i++) {
num += 1;
}
System.out.println("a+=1用时:" + (System.currentTimeMillis() - start));
}
private static void test3(long num, long size) {
long start = System.currentTimeMillis();
for (long i = 0; i < size; i++) {
num++;
}
System.out.println("a++用时:" + (System.currentTimeMillis() - start));
}
}结果a=a+1用时:4551
a+=1用时:4535
a++用时:4512
请问语句a=a*b和a*=b哪个运算速度快?
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