Java各种非空判断常用API

String str = " \t \n \f \r";
if (str == null || "".equals(str)) {
    System.out.println(str);
}

//isEmpty——value.length == 0
if (str == null || str.isEmpty()) {
    System.out.println(str);
}

//str == null || "".equals(str)
boolean flag = org.springframework.util.StringUtils.isEmpty(str);
System.out.println(flag);

//cs == null || cs.length() == 0——常用
flag = org.apache.commons.lang3.StringUtils.isEmpty(str);
System.out.println(flag);

//!isEmpty(cs)
flag = org.apache.commons.lang3.StringUtils.isNotEmpty(str);
System.out.println(flag);

//cs == null || cs.length() == 0 || 空白字符(空格"\t \n \f \r")
flag = org.apache.commons.lang3.StringUtils.isBlank(str);
System.out.println("isBlank:" + flag);

//!isBlank(cs)
flag = org.apache.commons.lang3.StringUtils.isNotBlank(str);
System.out.println(flag);

List list = new ArrayList();

//collection == null || collection.isEmpty()-size() == 0
flag = org.springframework.util.CollectionUtils.isEmpty(list);
System.out.println("list:" + flag);

Map map = new HashMap();
//cs == null || cs.length() == 0 collection == null || collection.isEmpty()-size() == 0
//array == null || array.length == 0 map == null || map.isEmpty()-没有k-v
flag = org.springframework.util.ObjectUtils.isEmpty(map);
System.out.println(flag);

Object obj = null;
//为false抛异常
org.springframework.util.Assert.isTrue(true, "抛异常");

//obj != null
org.springframework.util.Assert.isNull(obj, "字段非空");

//obj == null
org.springframework.util.Assert.notNull(map, "字段为空");

//collection == null || collection.isEmpty()
//array == null || array.length == 0 map == null || map.isEmpty()-没有k-v
org.springframework.util.Assert.notEmpty(list, "字段为空或空值");

jar引入

Maven地址：Maven Repository: Search/Browse/Explore (mvnrepository.com)

<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>5.1.7.RELEASE</version>
</dependency>

<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.4</version>
</dependency>