Java如何知道arraylist是否包含值对象的属性[重复]

Question

我想知道ArrayList网格中的属性

public class Grid {
  public int numb;

  public GridSeg(int numb) {
    this.numb = numb;
  }
}

public ArrayList<Grid> grids = new ArrayList<Grid>();

for (int i = 0; i < 6; i++) {
  Grid grid = new Grid(i);
  grids.add(grid);
}

/pseudo code since I don't know how it is done
if (grids.numb.contains(12)) {
  if (grid.numb == 12) //get grid index
}

Answer 1

你可以用流来实现它

    ArrayList<Grid> grids = new ArrayList<>();
    Grid grid = grids.stream().filter(l -> l.numb == 12).findFirst().orElse(null);
    int index = grids.indexOf(grid);