黑马程序员 【】java学习之路——反射——修改字段

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需求：通过反射的方式把某个类的String 类型的变量的值中的 ‘a’改成‘b’

<span style="font-size:18px;"><span style="font-size:18px;">package test;

public class ReflectPoint {
private int x;
public int y;

public String str1 = "basketball";
public String str2 = "envriement";
public String str3 = "bbbcccbbbbbbbbb";
public ReflectPoint(int x, int y) {
super();
this.x = x;
this.y = y;
}
@Override
public String toString()
{
return str1+"::"+str2+"::"+str3;
}

}
</span></span>

<span style="font-size:18px;"><span style="font-size:18px;">package test;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.util.*;
public class ReflaectTest {
public static void main(String[] args  ) throws  Exception {
ReflectPoint pt1 = new ReflectPoint(3,5);
Field fieldy = pt1.getClass().getField("y");
System.out.println(fieldy.get(pt1));
Field fieldx = pt1.getClass().getDeclaredField("x");
fieldx.setAccessible(true);
System.out.println(fieldx.get(pt1));

 changeStringValue(pt1);
 System.out.println(pt1);
}

private static void changeStringValue(Object obj) throws  Exception  {
Field [] fields = obj.getClass().getFields();
for (Field field : fields) {
//判断字段类型是否为String类型，如果是则替换
if (field.getType()== String.class) {
String oldValue = (String)field.get(obj);
String newValue = oldValue.replace('b', 'a');
field.set(obj, newValue);

}
}

} 
}</span></span>