java - 使用 -Xlint :unchecked for detail error in java 重新编译

Question

我有以下错误，但我似乎不知道如何调试它:

Note: MyStack.java uses unchecked or unsafe operations.

Note: Recompile with -Xlint:unchecked for details.

public class MyStack<T> implements MyStackInterface<T>{
        private T[] s;
        private int size;

    public MyStack() {
        this.s = (T[])new Object[30];
    }
        
    public void push(T x){
            if (size==s.length){
                T[] b = (T[])new Object[size*2];
                int i;
                for (i=0;i<s.length;i++){
                    b[i] = s[i];
                }
                s=b;
            }
            s[size++] = x;
        }
    public T pop(){
            if (size == 0){
                throw new RuntimeException("Stack Underflow");
            }
            return s[--size];
        }
    public T peek(){
            if (size==0) throw new RuntimeException("Stack Underflow");
            return s[size-1];
        }

    public boolean isEmpty(){
            return size==0;
        }
    public int size(){
            return size;
        }
}

Answer 1

编译代码时使用:

javac -Xlint:unchecked

然后你会看到:

MyStack.java:6: warning: [unchecked] unchecked cast
    this.s = (T[])new Object[30];
                  ^
  required: T[]
  found:    Object[]
  where T is a type-variable:
     T extends Object declared in class MyStack\

MyStack.java:11: warning: [unchecked] unchecked cast
            T[] b = (T[])new Object[size*2];
                         ^
  required: T[]
  found:    Object[]
  where T is a type-variable:
    T extends Object declared in class MyStack
2 warnings

最重要的是，问题是由于泛型类型数组的创 build 成的。要解决此问题，请阅读此链接:https://stackoverflow.com/a/530289/588532