JAVA笔试错题1

1)输出false是(C)

• Integer i01=59;
• int i02=59;
• Integer i03=Integer.valueOf(59);
• Integer i04=new Integer(59);

*A  System.out.println(i01==i02);

*B System.out.println(i01==i03);

*C  System.out.println(i03==i04);

*D  System.out.println(i02==i04);

解析
Byte,Short,Integer,Long,Character这5种整型的包装类也只是在对应值小于等于127并且大于等于-128时才可使用常量池，因为他们至占用一个字节(-128~127);

image.png

public class Test1 {
    public static void main(String[] args) {
        Integer a = 127;
        Integer b = 127;

        Integer c = 128;
        Integer d = 128;
        System.out.println(a == b);
        System.out.println(c == d);
        System.out.println(c == 128);
    }
    /*true
      false
      true*/
}