What are the limitations of Java generics?

1. Type variables in the static context of generic classes are invalid.

    //静态域或者方法里不能引用类型变量
    private static T instance;
    //静态方法 本身是泛型方法就行
    private static <T> T getInstance(){
    }

2. Type variables cannot be instantiated.

//    public Restrict() {
//        this.data = new T();
//    }

3. Generic parameters cannot be instantiated with basic types.

//      NormalGeneric<double> normalGeneric = new NormalGeneric<>();
        NormalGeneric<Double> normalGeneric = new NormalGeneric<>();

4. Arrays of parameterized types cannot be created.

Restrict<Double>[] restrictArray;
  Restrict<Double>[] restricts = new Restrict<Double>[10];

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