定义一个测试接口：

public interface IContent {
int getValue();
void f();
}

然后可以在方法体里面直接返回return new IContent()

public class InternalClass {
public IContent getContent(){
    return new IContent(){
        private int value ;
        private int v2;
        {
            value = 12;
            v2 = 10;
        }
        public int getValue(){return value + v2;}
        public void f(){System.out.println("noname class invoke f method!");}
    };
}

}