String s1="wanna";char[] a=new char[20];a[0]='w'-' ';a[1]='a';a[2]='n';a[3]='n';a[4]='a';String s2=String.valueOf(a);    System.out.println(s1);     System.out.println(s2);     System.out.println(s1.equals(s2));             為什么s1與s2不相等，應(yīng)該怎么改