Java 如何知道 arraylist 是否包含对象属性中的值

Question

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How to find an object in an ArrayList by property (8 个回答)

Get index of an arraylist using property of an contained object in java [duplicate] (3 个回答)

已关闭 3 年前。

我想查找该属性是否 numb在 ArrayList grids是否包含某个值。然后我想获取包含该值的条目的索引。

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

您可以通过流来实现

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