有如下代码：public class Test{ public static void main(String args[]) { String str = new String("World"); char ch[] = {'H','e','l','l','o'}; change(str,ch); System.out.println(str + "and" + ch); } public static void change(String str, char ch[]) { str = "Changed"; ch[0] = ' C'; }}运行后输出的结果是： A: Changed and Cello B: World and Cello C: World and CelloChanged and Hello D: World and Hello

public class Example { String str = new String("Java"); StringBuffer sb = new StringBuffer("C#"); public void strcat(String str, StringBuffer sb) { str = str + " study"; sb = sb.append(" exam"); } public static void main(String args[]) { Example ex = new Example(); ex.strcat(ex.str, ex.sb); System.out.println(ex.str); System.out.println(ex.sb); }}程序的输出结果是：______

有如下代码： public class Test{ public static void main(String args[]) { String str = new String("World"); char ch[] = {'H','e','l','l','o'}; change(str,ch); System.out.println(str + "and" + ch); } public static void change(String str, char ch[]) { str = "Changed"; ch[0] = 'C'; } } 运行后输出的结果是：

下列代码执行结果是?（ ） class HelloWorld { public static void modifyString(final String str) { str = "Hello World!"; } public static void main(String[] args) { String a = new String("Hello Java"); modifyString(a); System.out.println(“a = ” + a); } } A: a = Hello Java B: a = Hello World C: 代码编译错误 D: 运行时异常

下列程序的运行结果是（）public class Test {public static void main(String[] args) {String str = NULL;System.out.println(str);}} A: