JAVA题库:格林模拟试题二（下）6

　　Question 48)
　　Given the following variables
　　char c = ’c’;int i = 10;double d = 10;long l = 1;String s = "Hello";
　　Which of the following will compile without error?
　　1)c=c+i;
　　2)s+=i;
　　3)i+=s;
　　4)c+=s;
　　Question 49)
　　Which of the following will compile without error?
　　1) File f = new File("/","autoexec.bat");
　　2) DataInputStream d = new DataInputStream(System.in);
　　3) OutputStreamWriter o = new OutputStreamWriter(System.out);
　　4) RandomAccessFile r = new RandomAccessFile("OutFile");
　　Question 50)
　　Given the folowing classes which of the following will compile without error?
　　interface IFace{}class CFace implements IFace{}class Base{}public class ObRef extends Base{    public static void main(String argv[]){        ObRef ob = new ObRef();        Base b = new Base();        Object o1 = new Object();        IFace o2 = new CFace();    }}
　　1)o1=o2;
　　2)b=ob;
　　3)ob=b;
　　4)o1=b;
　　Question 51)
　　Given the following code what will be the output?
　　class ValHold{        public int i = 10;}public class ObParm{public static void main(String argv[]){        ObParm o = new ObParm();        o.amethod();        }        public void amethod(){                int i = 99;                ValHold v = new ValHold();                v.i=30;                another(v,i);                System.out.print( v.i );        }//End of amethod        public void another(ValHold v, int i){                i=0;                v.i = 20;                ValHold vh = new ValHold();                v =  vh;                System.out.print(v.i);        System.out.print(i);        }//End of another}
　　1) 10030
　　2) 20030
　　3) 209930
　　4) 10020