java - 在for循环java中跟踪前一个i

Question

我试图在 for 循环中获取当前i值和上一个值。i那可能吗？

public void mousePressed() {  
  for (int i = 0; i < 6; i++) {
    if (mouseX > boxes[i].x) {
      boxes.[i].openIt();
    }
  }
}

如果我打印i，我将得到当前值i

System.out.println(i);

如何打印之前的值i？我不想使用i-1，因为我在我的项目中使用随机数。

Answer 1

int i= -1;
int prev= -1;
boolean cond = true;
public void mousePressed() {  
    while(cond){
        i=myPositiveRNG.nextInt();//assuming positive numbers, 'cause it's an array index.
        if(prev>-1){
            System.out.println(prev);
        }
        if (mouseX > boxes[i].x){
            boxes.[i].openIt();
        }
        prev = i;
        cond=isItTimeToGo();
}

根据您的需要定制。

Answer 2

这可能是最直接的方法：

public void mousePressed() {
  int lastProcessedI = -1;//Or some reasonable default value
  for (int i = 0; i < 6; i++) {
    System.out.println("On iteration " + i + " having completed " + lastProcessedI);
    if (mouseX > boxes[i].x) {
      boxes.[i].openIt();
    }
    lastProcessedI = i;//mark i as having been processed.
  }
}

请注意，lastProcessedI应该在您的 for 循环之前声明，否则循环迭代时它将超出范围。通过在 for 循环之前声明它，它会停留在mousePressed方法的包含范围内。

如果您需要维护更多历史记录，这也很容易实现：

public void mousePressed() {
  List<Integer> processHistory = new ArrayList<Integer>();
  for (int i = 0; i < 6; i++) {
    System.out.println("On iteration " + i + " having completed " + processHistory.get(processHistory.size() - 1));
    if (mouseX > boxes[i].x) {
      boxes.[i].openIt();
    }
    processHistory.add(i);//store i as having been processed.
  }

  //here you can get any previously processed i
  processHistory.get(processHistory.size() - 2);//I selected 2 arbitrarily, but it will provide the second-to-last i processed.
}