1,equals
@test
public void test_equal(){
string a="1";
int b=1;
boolean result=a.equals(b);
system.out.println(result);
}
我以为会报错的,因为类型不同啊,一个是字符串,一个是整型. 结果没有报错.
原因:equals 比较时自动把基本类型转化为包装类型了
运行结果是:
false
应该改为:
boolean result=a.equals(string.valueof(b));
2,包装类型
public void test_equal2(){
long a=229l;
long b=229l;
system.out.println((a==b));
运行结果:false
long a=29l;
long b=29l;
运行结果为:true
system.out.println((a.intvalue()==b.intvalue()));
3,把json字符串反序列化为对象
当json字符串是空时竟然不报错,示例如下:
objectmapper mapper = new objectmapper();
student2 student;
try {
student = mapper.readvalue("{}", student2.class);
system.out.println(student.getclassroom());
system.out.println(student.getschoolnumber());
} catch (exception e) {
e.printstacktrace();
}
运行结果:
但是,如果json字符串中包含的属性,对象中没有则报错
student = mapper.readvalue("{\"username2323\":\"whuang\"}", student2.class);
student2类中没有属性username2323
报错信息:
org.codehaus.jackson.map.exc.unrecognizedpropertyexception: unrecognized field "username2323" (class tv_mobile.student2), not marked as ignorable
at [source: java.io.stringreader@7bb613c0; line: 1, column: 18] (through reference chain: tv_mobile.student2["username2323"])
at org.codehaus.jackson.map.exc.unrecognizedpropertyexception.from(unrecognizedpropertyexception.java:53)
http://blog.csdn.net/hw1287789687/article/details/45916001
作者:黄威