Java Programming

Hello,

I was playing with benchmarks in a standard configured eclipse (idk1.6.0_10).
And in this forum I've read a lot that micro optimization is not needed as the compiler does that for you.
But I got the following results:

^= time: 1813
=! time: 3172

when running this code

public class ShiftTrue {
	public static void main(String[] args) {
		boolean tmp=true;
		long startTime = System.currentTimeMillis();
		
		for (int i=0;i<Integer.MAX_VALUE;i++){
			tmp^=true;
		}
		System.out.println("^= time: "+
				(System.currentTimeMillis()-startTime));
		
		startTime = System.currentTimeMillis();
		for (int i=0;i<Integer.MAX_VALUE;i++){
			tmp=!tmp;
		}
		System.out.println("=! time: "+
				(System.currentTimeMillis()-startTime));
	}
}

So my finding is that the compiler is pretty bad at optimize as the time elapsed should have been the same.
I also have example of two other benchmarks i did.
Result:

Shifted: 62 millis
Divided: 63 millis

When running:

public class bitshift {
	public static void main(String[] args) {
		long startTime = System.currentTimeMillis();
		int a = 0;
		for(int i = 1; i<100000000;i++){
			a = 1029 >>> 8;
		}
		System.out.println("Shifted: "+
				(System.currentTimeMillis()-startTime)+" millis");
		startTime = System.currentTimeMillis();
		for(int i = 1; i<100000000;i++){
			a = 1029/256;
		}
		System.out.println("Divided: "+
				(System.currentTimeMillis()-startTime)+" millis");
	}
}

Time elapsed should be 0 as the loop should only be run one time.
When using "i" in the loop I got the following:

Shifted: 94 millis
Divided: 1172 millis

Code:

public class bitshift {
	public static void main(String[] args) {
		long startTime = System.currentTimeMillis();
		int a = 0;
		for(int i = 1; i<100000000;i++){
			a = i >>> 8;
		}
		System.out.println("Shifted: "+
				(System.currentTimeMillis()-startTime)+" millis");
		startTime = System.currentTimeMillis();
		for(int i = 1; i<100000000;i++){
			a = i/256;
		}
		System.out.println("Divided: "+
				(System.currentTimeMillis()-startTime)+" millis");
	}
}

Also pretty bad at optimize as the time elapsed should have been the same.
Are there any way to tell the compiler in eclipse to do a better job or do I have to think about those optimizations myself even if they logically should be no problem for the compiler to fix.