?? stackvars.java
字號:
class StackVars
{
private int instVar;
private static int staticVar;
//stack variable access
void stackAccess(int val)
{
int j=0;
for (int i=0; i<val; i++)
j += 1;
}
//class instance variable access
void instanceAccess(int val)
{
for (int i=0; i<val; i++)
instVar += 1;
}
//class static variable access
void staticAccess(int val)
{
for (int i=0; i<val; i++)
staticVar += 1;
}
public static void main(String args[])
{
StackVars t = new StackVars();
long start = System.currentTimeMillis();
for (int i=0; i<100; i++)
t.stackAccess(1000000);
long end = System.currentTimeMillis();
System.out.println("loop with stack vars " + (end-start));
long num=end-start;
start = System.currentTimeMillis();
for (int i=0; i<100; i++)
t.instanceAccess(1000000);
end = System.currentTimeMillis();
System.out.println("loop with instance vars " + (end-start));
num=(end-start)/num;
start = System.currentTimeMillis();
for (int i=0; i<100; i++)
t.staticAccess(1000000);
end = System.currentTimeMillis();
System.out.println("loop with static vars " + (end-start));
System.out.println("stack is " + num + " times faster than " +
"instance");
}
}
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