package test;

public class Point1 {

    private int x;

    public int y;

    public String a="asdasd";

    public Point1() {}

    public Point1(int i, int j) {

        super();

        this.x=i;

        this.y=j;

    }

}

public class fieldTest {

    public static void main(String[] args) throws  Exception {

        Point1 point=new Point1(, );

        Field fieldY=point.getClass().getField("y");      //  y字段公有

        System.out.println(fieldY);

        System.out.println(fieldY.get(point));

        Field fieldX=point.getClass().getDeclaredField("x");   //x字段私有

        fieldX.setAccessible(true);                            //AccessibleTest类中的成员变量为private,故必须进行此操作

        System.out.println(fieldX.get(point));                 //如果没有在获取Field之前调用setAccessible(true)方法，异常

        Point1 point2=new Point1();

        Field[] fields=point.getClass().getFields();          //把Point1函数中的String字段做改动

        for(Field field:fields) {

            if (field.getType()==String.class) {

                String oldValue =(String) field.get(point2);

                String newVaule =oldValue.replace('a', 'b');

                field.set(point2, newVaule);

                System.out.println(field.get(point2));

            }

        }

    }

}

输出结果

public int test.Point1.y

bsdbsd