【错误记录】Groovy 注入方法报错 ( Cannot add new method [hello] for arguments [[]]. It already exists )

class Student {
    def name;

    def hello() {
        println "Hello " + name
    }
}

// 向 Student 类注入 hello 方法
Student.metaClass.hello << {
    println delegate
    println "Hello ${delegate.name}"
}

Caught: groovy.lang.GroovyRuntimeException: Cannot add new method [hello] for arguments [[]]. It already exists!
groovy.lang.GroovyRuntimeException: Cannot add new method [hello] for arguments [[]]. It already exists!
	at Groovy.run(Groovy.groovy:11)