java程序题

public class Test {
    public static void main(String[] args) {
        Person person=new Person("张三");
        change(person);
        System.out.println(person.name);
    }
    public static void change(Person person) {
        Person person2=new Person("李四");
        person=person2;
    }
}
public class Person {
    String name;
    public Person(String name) {
        this.name = name;
    }
}

public class Test2 {
    public static void main(String[] args) {
        Thread thread=new Thread() {
            public void run() {
                pong();
            }
        };
        thread.run();
        System.out.print("ping");
    }
    public static void pong() {
        System.out.print("pong");
    }
}

public static int getIndexOfArray(float[] f) {
        int rtn=-1;
        float objf=3.4;
        List list=null;
        for (int i = 0; i < f.size(); i++) {
            list.add(f[i]);
        }
        for (int i = 0; i < list.size(); i++) {
            float temp=(float) list.get(i);
            if(objf==temp) {
                rtn=i;
            }
        }
        return rtn;
    }