public class SafeArray { private int[] arr; public SafeArray() { this(10); // 預設 10 個元素 } public SafeArray(int length) { arr = new int[length]; } public void showElement() { for(int i : arr) { System.out.print(i + " "); } } public int getElement(int i) { if(i >= arr.length || i < 0) { System.err.println("索引錯誤"); return 0; } return arr[i]; } public int getLength() { return arr.length; } public void setElement(int i, int data) { if(i >= arr.length || i < 0) { System.err.println("索引錯誤"); return; } arr[i] = data; } }