java - 如何在Java中调试 “illegal start of expression”？

Question

在Jcreator中，这里有12个错误，我不知道如何解决。它说“非法开始expr ....”。

如果我更改某些内容，突然会有50个错误。

public class Practica_figura {
    Class Figura() {
        private float base;
        private float altura;
        private float radio;
    }

    public void asignar(float ba, float al, float ra) {
        base = ba;
        altura = al;
        radio = ra;
    }

    class Cuadrado extends Figura()
    {
        private float base;
        private float altura;

        public void calcular_area(float b, float a) {
            float res = base * altura;
        }

        public void calcular_perimetro(float a) {
            float resp = 4 * a;
        }

        public void rareac() {
            return area;
        }

        public void rperic() {
            return perimetro;
        }
    }

    class Triangulo extends Figura()
    {
        private float base;
        private float altura;
        private float la;
        private float lb;
        private float lc;

        public void asignar(float a, float b, float c) {
            la = a;
            lb = b;
            lc = c;
        }

        public void calcular_area(float b, float a) {
            float res = (base * altura) / 2;
        }

        public void calcular_perimetro(float a) {
            float resp = 4 * a;
        }

        public void rareat() {
            return area;
        }

        public void rperit() {
            return perimetro;
        }

    }

    public static void main(String[] args) {
        // TODO code application logic here

        float base = 0, altura = 0, radio = 0;
        JOptionPane.showMessageDialog(null, "Programa para calcular área y perímetro");
    }
}

Answer 1

进行正确的类定义更改
public class Practica_figura { Class Figura(){
至
public class Figura{
我不太了解您要执行的操作，如果您想要的是构造函数，则必须添加:

public Figura(){
}