Java createOperate方法不能声明为静态；静态方法只能在静态或顶级类型中声明

问题是：createOperate方法不能声明为静态；静态方法只能在静态或顶级类型中声明

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我不知道如何解决。谢谢

正如错误消息明确指出的那样，您有3个选项：

将

createOperate

方法更改为非静态

将

操作工厂

类更改为静态

将静态方法

createOperate

移动到封闭的

Welcome

类中

public class Welcome {
    public class OperationFactory {

        public static Operation createOperate(String operate) {
            Operation operation = null;
            if("+".equalsIgnoreCase(operate)) {
                operation = new OperationAdd();
            }else if("-".equalsIgnoreCase(operate)) {
                operation = new OperationSub();
            }else if("*".equalsIgnoreCase(operate)) {
                operation = new OperationMul();
            }else {
                operation = new OperationDiv();
            }
            return operation;
        }
    }
}