Java 中 String的三种判断方式NotEmpty，NotNull和@NotBlank的区别

1.@NotNull：不能为null，但可以为empty
(""," ","   ")      

2.@NotEmpty：不能为null，而且长度必须大于0
(" ","  ")

3.@NotBlank：只能作用在String上，不能为null，而且调用trim()后，长度必须大于0
("test")    即：必须有实际字符


@NotNull: The CharSequence, Collection, Map or Array object is not null,
but can be empty.

@NotEmpty: The CharSequence, Collection, Map or Array object is not null
and size > 0.

@NotBlank: The string is not null and the trimmed length is greater than
zero.

4.examples:
1.String name = null;

	@NotNull: false
	@NotEmpty:false 
	@NotBlank:false 

2.String name = "";

	@NotNull:true
	@NotEmpty: false
	@NotBlank: false

3.String name = " ";

	@NotNull: true
	@NotEmpty: true
	@NotBlank: false

4.String name = "Great answer!";

	@NotNull: true
	@NotEmpty:true
	@NotBlank:true