Example code for passing and returning objects in Java

1. The Clone() method generates an object, and the object must be assigned after using the method.

Vector v2 = (Vector)v.clone();

2. The Clone() method is a protected type method in object. If the class you create needs to use the Clone() method, you need to rewrite it yourself and inherit the Cloneable interface.

package tweleve;import java.util.*;class MyObject implements Cloneable {int i;

    MyObject(int ii) {
        i = ii;
    }public Object clone() {
        Object object = null;try {
            object = super.clone();
        } catch (CloneNotSupportedException e) {
            System.out.println("MyObject can't clone");
        }return object;
    }public String toString() {return Integer.toString(i);
    }
}public class LocalCopy {static MyObject g(MyObject v) {
        v.i++;return v;
    }static MyObject f(MyObject v) {
        v = (MyObject) v.clone();
        v.i++;return v;
    }public static void main(String[] args) {
        MyObject aMyObject = new MyObject(11);
        MyObject bMyObject = g(aMyObject);if (aMyObject == bMyObject)
            System.out.println("a==b");elseSystem.out.println("a!=b");
        System.out.println("a=" + aMyObject);
        System.out.println("b=" + bMyObject);
        MyObject cMyObject = new MyObject(31);
        MyObject dMyObject = f(cMyObject);if (cMyObject == dMyObject)
            System.out.println("c==d");elseSystem.out.println("c!=d");
        System.out.println("c=" + cMyObject);
        System.out.println("d=" + dMyObject);

    }

}

3. If you want a class to be cloned, you need to follow the following steps: (1) Implement the Cloneable interface

                                            lone() method

                                                                                                                       (4) Capture violations in your own clone()

4. All objects in the String class Methods that can modify String actually create and return a new String class. The original String class has not changed, including + and +=. StringBuffer is more efficient than String when operating strings.

package tweleve;import java.sql.Ref;import org.omg.CORBA.SystemException;public class Stringer {static String upcase(String s){         return s.toUpperCase();
    }    public static void main(String[] args){
        String qString=new String("howdy");
        System.out.println(qString);
        String qq=upcase(qString);
        System.out.println(qq);
        System.out.println(qString);
    }

}

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