Hello everyone, today I will share about the tip of checking String null or full space conveniently
I will use the library StringUtils class to download the jar file to import into the library at ( link )
If you use maven project, it’s easier, just import in pom.xml file
1 2 3 4 5 6 7 | <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 --> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.7</version> </dependency> |
If you want to check if the String is null / full space / empty, then manually check will be like this
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | <span class="token keyword">package</span> test <span class="token punctuation">;</span> <span class="token keyword">import</span> <span class="token namespace">org <span class="token punctuation">.</span> apache <span class="token punctuation">.</span> commons <span class="token punctuation">.</span> lang3</span> <span class="token punctuation">.</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">;</span> <span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">Main</span> <span class="token punctuation">{</span> <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span> <span class="token punctuation">(</span> <span class="token class-name">String</span> <span class="token punctuation">[</span> <span class="token punctuation">]</span> args <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token class-name">String</span> a <span class="token operator">=</span> <span class="token keyword">null</span> <span class="token punctuation">;</span> <span class="token class-name">String</span> b <span class="token operator">=</span> <span class="token string">""</span> <span class="token punctuation">;</span> <span class="token class-name">String</span> c <span class="token operator">=</span> <span class="token string">" "</span> <span class="token punctuation">;</span> <span class="token class-name">System</span> <span class="token punctuation">.</span> out <span class="token punctuation">.</span> <span class="token function">println</span> <span class="token punctuation">(</span> <span class="token string">"manual result: "</span> <span class="token operator">+</span> <span class="token string">"a: "</span> <span class="token operator">+</span> <span class="token function">validateStringManual</span> <span class="token punctuation">(</span> a <span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">" b: "</span> <span class="token operator">+</span> <span class="token function">validateStringManual</span> <span class="token punctuation">(</span> b <span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">" c: "</span> <span class="token operator">+</span> <span class="token function">validateStringManual</span> <span class="token punctuation">(</span> c <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token class-name">Boolean</span> <span class="token function">validateStringManual</span> <span class="token punctuation">(</span> <span class="token class-name">String</span> str <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">if</span> <span class="token punctuation">(</span> <span class="token function">length</span> <span class="token punctuation">(</span> str <span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token number">0</span> <span class="token operator">||</span> <span class="token function">isFullspace</span> <span class="token punctuation">(</span> str <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> <span class="token boolean">true</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">return</span> <span class="token boolean">false</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">int</span> <span class="token function">length</span> <span class="token punctuation">(</span> <span class="token class-name">CharSequence</span> cs <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> cs <span class="token operator">==</span> <span class="token keyword">null</span> <span class="token operator">?</span> <span class="token number">0</span> <span class="token operator">:</span> cs <span class="token punctuation">.</span> <span class="token function">length</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token class-name">Boolean</span> <span class="token function">isFullspace</span> <span class="token punctuation">(</span> <span class="token class-name">CharSequence</span> cs <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">int</span> strLen <span class="token operator">=</span> <span class="token function">length</span> <span class="token punctuation">(</span> cs <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token keyword">for</span> <span class="token punctuation">(</span> <span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span> <span class="token punctuation">;</span> i <span class="token operator"><</span> strLen <span class="token punctuation">;</span> <span class="token operator">++</span> i <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">if</span> <span class="token punctuation">(</span> <span class="token operator">!</span> <span class="token class-name">Character</span> <span class="token punctuation">.</span> <span class="token function">isWhitespace</span> <span class="token punctuation">(</span> cs <span class="token punctuation">.</span> <span class="token function">charAt</span> <span class="token punctuation">(</span> i <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> <span class="token boolean">false</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span> <span class="token keyword">return</span> <span class="token boolean">true</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span> |
Output
1 2 | manual result: a: true b: true c: true |
Very long and messy, right?
Now if we use the library, we just need to do this
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | <span class="token keyword">package</span> test <span class="token punctuation">;</span> <span class="token keyword">import</span> <span class="token namespace">org <span class="token punctuation">.</span> apache <span class="token punctuation">.</span> commons <span class="token punctuation">.</span> lang3</span> <span class="token punctuation">.</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">;</span> <span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">Main</span> <span class="token punctuation">{</span> <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span> <span class="token punctuation">(</span> <span class="token class-name">String</span> <span class="token punctuation">[</span> <span class="token punctuation">]</span> args <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token class-name">String</span> a <span class="token operator">=</span> <span class="token keyword">null</span> <span class="token punctuation">;</span> <span class="token class-name">String</span> b <span class="token operator">=</span> <span class="token string">""</span> <span class="token punctuation">;</span> <span class="token class-name">String</span> c <span class="token operator">=</span> <span class="token string">" "</span> <span class="token punctuation">;</span> <span class="token class-name">System</span> <span class="token punctuation">.</span> out <span class="token punctuation">.</span> <span class="token function">println</span> <span class="token punctuation">(</span> <span class="token string">"StringUtils result: "</span> <span class="token operator">+</span> <span class="token string">"a: "</span> <span class="token operator">+</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">.</span> <span class="token function">isBlank</span> <span class="token punctuation">(</span> a <span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">" b: "</span> <span class="token operator">+</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">.</span> <span class="token function">isBlank</span> <span class="token punctuation">(</span> a <span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">" c: "</span> <span class="token operator">+</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">.</span> <span class="token function">isBlank</span> <span class="token punctuation">(</span> c <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span> |
Output
1 2 | StringUtils result: a: true b: true c: true |
Still the same, very convenient, right?
If you do not want to check the fullspace, use the following method:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | <span class="token keyword">package</span> test <span class="token punctuation">;</span> <span class="token keyword">import</span> <span class="token namespace">org <span class="token punctuation">.</span> apache <span class="token punctuation">.</span> commons <span class="token punctuation">.</span> lang3</span> <span class="token punctuation">.</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">;</span> <span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">Main</span> <span class="token punctuation">{</span> <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span> <span class="token punctuation">(</span> <span class="token class-name">String</span> <span class="token punctuation">[</span> <span class="token punctuation">]</span> args <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token class-name">String</span> a <span class="token operator">=</span> <span class="token keyword">null</span> <span class="token punctuation">;</span> <span class="token class-name">String</span> b <span class="token operator">=</span> <span class="token string">""</span> <span class="token punctuation">;</span> <span class="token class-name">String</span> c <span class="token operator">=</span> <span class="token string">" "</span> <span class="token punctuation">;</span> <span class="token class-name">System</span> <span class="token punctuation">.</span> out <span class="token punctuation">.</span> <span class="token function">println</span> <span class="token punctuation">(</span> <span class="token string">"StringUtils result: "</span> <span class="token operator">+</span> <span class="token string">"a: "</span> <span class="token operator">+</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">.</span> <span class="token function">isEmpty</span> <span class="token punctuation">(</span> a <span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">" b: "</span> <span class="token operator">+</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">.</span> <span class="token function">isEmpty</span> <span class="token punctuation">(</span> a <span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">" c: "</span> <span class="token operator">+</span> <span class="token class-name">StringUtils</span> <span class="token punctuation">.</span> <span class="token function">isEmpty</span> <span class="token punctuation">(</span> c <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span> |
Output
1 2 | StringUtils result: a: true b: true c: false |
StringUtils has many other libraries that you can check and use for your purposes. For example, isNotBlank (), isNotEmpty () …
Now let’s move on to validate Collections in java
Maven project, then add this paragraph to pom.xml file:
1 2 3 4 5 6 7 8 | <!-- https://mvnrepository.com/artifact/org.apache.commons/commons-collections4 --> <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-collections4</artifactId> <version>4.1</version> </dependency> |
And java projects usually import jar file to download at the link
An example of checking whether that Collection is empty or null
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | <span class="token keyword">package</span> test <span class="token punctuation">;</span> <span class="token keyword">import</span> <span class="token namespace">org <span class="token punctuation">.</span> apache <span class="token punctuation">.</span> commons <span class="token punctuation">.</span> collections4</span> <span class="token punctuation">.</span> <span class="token class-name">CollectionUtils</span> <span class="token punctuation">;</span> <span class="token keyword">import</span> <span class="token namespace">java <span class="token punctuation">.</span> util</span> <span class="token punctuation">.</span> <span class="token class-name">ArrayList</span> <span class="token punctuation">;</span> <span class="token keyword">import</span> <span class="token namespace">java <span class="token punctuation">.</span> util</span> <span class="token punctuation">.</span> <span class="token class-name">List</span> <span class="token punctuation">;</span> <span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">Main</span> <span class="token punctuation">{</span> <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span> <span class="token punctuation">(</span> <span class="token class-name">String</span> <span class="token punctuation">[</span> <span class="token punctuation">]</span> args <span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token class-name">List</span> <span class="token generics"><span class="token punctuation"><</span> <span class="token class-name">String</span> <span class="token punctuation">></span></span> list1 <span class="token operator">=</span> <span class="token keyword">null</span> <span class="token punctuation">;</span> <span class="token class-name">List</span> <span class="token generics"><span class="token punctuation"><</span> <span class="token class-name">String</span> <span class="token punctuation">></span></span> list2 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span> <span class="token generics"><span class="token punctuation"><</span> <span class="token punctuation">></span></span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token class-name">List</span> <span class="token generics"><span class="token punctuation"><</span> <span class="token class-name">String</span> <span class="token punctuation">></span></span> list3 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ArrayList</span> <span class="token generics"><span class="token punctuation"><</span> <span class="token punctuation">></span></span> <span class="token punctuation">(</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> list3 <span class="token punctuation">.</span> <span class="token function">add</span> <span class="token punctuation">(</span> <span class="token string">"xxx"</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token class-name">System</span> <span class="token punctuation">.</span> out <span class="token punctuation">.</span> <span class="token function">println</span> <span class="token punctuation">(</span> <span class="token string">"result: "</span> <span class="token operator">+</span> <span class="token string">"list1: "</span> <span class="token operator">+</span> <span class="token class-name">CollectionUtils</span> <span class="token punctuation">.</span> <span class="token function">isEmpty</span> <span class="token punctuation">(</span> list1 <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token class-name">System</span> <span class="token punctuation">.</span> out <span class="token punctuation">.</span> <span class="token function">println</span> <span class="token punctuation">(</span> <span class="token string">"result: "</span> <span class="token operator">+</span> <span class="token string">"list2: "</span> <span class="token operator">+</span> <span class="token class-name">CollectionUtils</span> <span class="token punctuation">.</span> <span class="token function">isEmpty</span> <span class="token punctuation">(</span> list2 <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token class-name">System</span> <span class="token punctuation">.</span> out <span class="token punctuation">.</span> <span class="token function">println</span> <span class="token punctuation">(</span> <span class="token string">"result: "</span> <span class="token operator">+</span> <span class="token string">"list3: "</span> <span class="token operator">+</span> <span class="token class-name">CollectionUtils</span> <span class="token punctuation">.</span> <span class="token function">isEmpty</span> <span class="token punctuation">(</span> list3 <span class="token punctuation">)</span> <span class="token punctuation">)</span> <span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span> |
Output
1 2 3 4 | result: list1: true result: list2: true result: list3: false |
This is just one of the functions of the CollectionUtils class, depending on the purpose of the use you get to use.
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