现有:public class Tester {public static void main(String[] args) {int x = 5;Integer x1 = x;Integer x2 = x;int x3 = new Integer(5);System.out.print(x1.equals(x));System.out.print(x1 == x);System.out.print(x2.equals(x1));System.out.print(x2 == x1);System.out.print(x2 == x3);System.out.print(x2.equals(x3));}}结果为:
A. 编译失败
B. falsefalsetruetruetruetrue
C. truetruetruetruetruetrue
D. falsefalsetruetruetruefalse
E. truefalsetruefalsefalsetrue
F. 运行时异常被抛出
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String foo="blue";boolean[] bar=new boolean[1];if(bar[0]){foo="green";}foo的值是多少? ( )
A. ""
B. null
C. blue
D. green
int index=1;String[] test=new String[3];String foo=test[index];foo的值是多少? ( )
A. ""
B. null
C. throw Exception
D. not compile
若变量s是String类型的数据,那么表达式(s+s)的类型是()
A. char
B. string
C. int
D. long
若有定义String answer ="少年强则国强!";则answer.length()的值是()
A. 7
B. 8
C. 9
D. 14