如何用java实现30选7

用随机数就可以实现：
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Pick7In30 {
public static void main(String[] args) {
List<Integer> numbers = new ArrayList<Integer>(30);
int[] results = new int[7];
for (int i = 0; i < 30; i++) {
numbers.add(i + 1);
}

for (int i = 0; i < 7; i++) {
int index = pick(30 - i);
results[i] = numbers.get(index - 1);
numbers.remove(index - 1);
}

Arrays.sort(results);

for (int i = 0; i < 7; i++) {
System.out.println(results[i]);
}
}

private static int pick(int capacity) {
return (int) (Math.floor(Math.random() * capacity)) + 1;
}
}