JAVA同类中的方法可以调用本类的成员变量吗？

[lipingqingqing]

事实上是可以的，但是我的一个程序出了点小问题，同类的方法访问不了该类的成员变量，贴出来给大家看一下：
import java.util.Scanner;

public class test {
public double a;
public double b;
public double c;
public double delta;

public void getvalue() {
Scanner sc = new Scanner(System.in);
System.out.print("输入a的值：");
double a = sc.nextDouble();

if (a==0) {
System.out.print("请重新输入a的值，a不等于0:");
a = sc.nextDouble();
}

System.out.print("输入b的值：");
double b = sc.nextDouble();
System.out.print("输入c的值：");
double c = sc.nextDouble();
panduan();

}

public void panduan() {
double x1, x2;
delta = b * b - 4 * a * c;
System.out.println(delta);
if (delta > 0) {
System.out.println("方程有两个不等实根");
x1 = -b + Math.sqrt(delta) / (2 * a);
x2 = -b - Math.sqrt(delta) / (2 * a);
System.out.println(x1);
System.out.println(x2);
} else if (delta == 0) {

System.out.println("方程有两个相等实根");
x1 = -b / (2 * a);
System.out.print(x1);
} else if (delta < 0) {
System.out.println("方程有两个虚根");
x1 = -b + Math.sqrt(-delta) / (2 * a);
x2 = -b - Math.sqrt(-delta) / (2 * a);
System.out.println(x1);
System.out.println(x2);
}

}
}
//主类
public class TestMain {

public static void main(String[] args) {
test test1=new test();
test1.getvalue();
}

}

[lacus87]

public void getvalue() {
Scanner sc = new Scanner(System.in);
System.out.print("输入a的值：");
double a= sc.nextDouble();

if (a==0) {
System.out.print("请重新输入a的值，a不等于0:");
a = sc.nextDouble();
}

System.out.print("输入b的值：");
double b = sc.nextDouble();
System.out.print("输入c的值：");
double c = sc.nextDouble();
panduan();

}

你这里定义的是局部变量，把红字的去掉就可以了

[ptcoding]

import java.util.Scanner;

class Test {
	public double a; 	//楼主开头这里已经
	public double b;	//定义了double类型的
	public double c;	//a，b，c变量了
	public double delta;

	public void getvalue() {
		Scanner sc = new Scanner(System.in);
		System.out.print("输入a的值：");
		double a = sc.nextDouble();//结果这里又重新定义了一个局部变量

		if (a == 0) {
			System.out.print("请重新输入a的值，a不等于0:");
			a = sc.nextDouble();
		}

		System.out.print("输入b的值：");
		double b = sc.nextDouble(); //结果这里又重新定义了一个局部变量
		System.out.print("输入c的值：");
		double c = sc.nextDouble();//结果这里又重新定义了一个局部变量
		panduan();

	}

	public void panduan() {
		double x1, x2;
		delta = b * b - 4 * a * c;
		System.out.println(delta);
		if (delta > 0) {
			System.out.println("方程有两个不等实根");
			x1 = -b + Math.sqrt(delta) / (2 * a);
			x2 = -b - Math.sqrt(delta) / (2 * a);
			System.out.println(x1);
			System.out.println(x2);
		} else if (delta == 0) {

			System.out.println("方程有两个相等实根");
			x1 = -b / (2 * a);
			System.out.print(x1);
		} else if (delta < 0) {
			System.out.println("方程有两个虚根");
			x1 = -b + Math.sqrt(-delta) / (2 * a);
			x2 = -b - Math.sqrt(-delta) / (2 * a);
			System.out.println(x1);
			System.out.println(x2);
		}

	}
}

这样赋值的时候只会把输入的值赋给你方法中定义的局部变量，而你在类中定义的全局变量并没有赋值，正确的做法是直接用全局变量，而不用重新在方法中定义a，b，c了

[lipingqingqing]

哦，对啊。原来是这里错了。谢谢各位，下次要小心了。

[yktd26]

你在方法中声明定义的变量是方法的局部变量，你要想赋值给类成员变量不要重新声明

a = sc.nextDouble();

而不是

double a = sc.nextDouble();

或者通过

public class test {
	public double a;


	public void getvalue() {
	
	double a = 5.0;
	System.out.println(a);
	System.out.println(this.a);
	

	}
	public static void main(String[] args) {
		test test1=new test();
		test1.getvalue();
	}
}

理解的更好一点