Google Guava学习计划第一章Guava Utilities—Preconditions_ComparisonChain_Strings_CharMatcher

1.preconditions 断言:在类似于条件解析时，进行一些重要的验证,验证为空。
2.ComparisonChain 编写比较器：采用ComparisonChain 以total,input,name 三者来排序,按照先后顺序
3.Strings 字符串的处理   repeat padEnd padStart  commonPrefix  commonsuffix
4.CharMatcher 字符的处理   removeFrom  retainFrom

以下是具体代码：

package Utilities;

import com.google.common.base.CharMatcher;
import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import com.google.common.collect.ComparisonChain;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import org.junit.Test;

import java.util.ArrayList;
import java.util.List;
import java.util.TreeSet;

import static org.hamcrest.core.IsEqual.equalTo;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;

/**
* ${DESCRIPTION}
* 1.preconditions 断言:在类似于条件解析时，进行一些重要的验证,验证为空。
* 2.ComparisonChain 编写比较器
* 3.Strings 字符串的处理
* 4.CharMatcher 字符的处理
* @author mengxp
* @version 1.0
* @create 2017-12-11 19:50
**/
public class Preconditions_ComparisonChain_Strings_CharMatcher {

//1.***********preconditions*******
@Test
public void testPreconditions_NotNull(){
List<String> var1=null;
Preconditions.checkNotNull(var1,"Collection should  not  be nullable...",var1);
}

@Test
public void testPreconditions_checkArgument(){
final String num="132";
Preconditions.checkArgument(num.equals("133"),"must be equals",num);
}
//检查数组的角标越界
@Test
public void testPreconditions_checkElementIndex(){
Preconditions.checkElementIndex(2,3,"max length is=2");
}

//3.************Strings********
@Test
public void testStringsRepeat(){
String var="mengxp";
String repeat = Strings.repeat(var, 2);
assertThat(repeat,equalTo("mengxpmengxp"));

String commonPrefix= Strings.commonPrefix("AAASS", "AAWW");
assertThat(commonPrefix,equalTo("AA"));

String commonSuffix= Strings.commonSuffix("AAASS", "AAWWSSS");
assertThat(commonSuffix,equalTo("SS"));

// padEnd(String string, int minLength, char padChar) 中minLength为结果的字符串的长度=string+(minlength-原stringLength)*padChar
String padEnd= Strings.padEnd("Jone", 6, 'x');
String padStart= Strings.padStart("78", 4, '0');

String empty= Strings.nullToEmpty(null
4000
);
assertThat(empty,equalTo(""));

String nulll = Strings.emptyToNull("");
assertThat(nulll,equalTo(null));

assertTrue(Strings.isNullOrEmpty(""));
}

//4.************CharMatcher 字符的处理************
@Test
public void testCharMatcher(){
assertThat(CharMatcher.javaDigit().matches('1'),equalTo(true));
//获取字符串中某个字符的个数
assertThat(CharMatcher.is('A').countIn("mengxp is good boy .got AAAAA"),equalTo(5));
assertThat(CharMatcher.breakingWhitespace().collapseFrom("meng xiao peng",'*'),equalTo("meng*xiao*peng"));
assertThat(CharMatcher.javaDigit().or(CharMatcher.whitespace()).removeFrom("hello 123 world"),equalTo("helloworld"));
assertThat(CharMatcher.javaDigit().or(CharMatcher.whitespace()).retainFrom("hello 123 world"),equalTo(" 123 "));
}

/**
* 2.ComparisonChain 编写比较器
*/
static class ComparisonChainObj implements Comparable<ComparisonChainObj>{
private int total;
private int input;
private int output;
private String name;

public ComparisonChainObj(int input, int output, String name) {
this.input = input;
this.output = output;
this.total=input-output;
this.name = name;
}

public int getTotal() {
return total;
}

public void setTotal(int total) {
this.total = total;
}

public int getInput() {
return input;
}

public void setInput(int input) {
this.input = input;
}

public int getOutput() {
return output;
}

public void setOutput(int output) {
this.output = output;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;

ComparisonChainObj that = (ComparisonChainObj) o;

if (total != that.total) return false;
if (input != that.input) return false;
if (output != that.output) return false;
return name.equals(that.name);
}

@Override
public int hashCode() {
int result = total;
result = 31 * result + input;
result = 31 * result + output;
result = 31 * result + name.hashCode();
return result;
}

//采用ComparisonChain 以total,input,name 三者来排序,按照先后顺序
@Override
public int compareTo(ComparisonChainObj o) {
return ComparisonChain.start().compare(this.total,o.getTotal())
.compare(this.input,o.getInput())
.compare(this.name,o.getName()).result();
}

public static void main(String[] args) {
ComparisonChainObj var1=new ComparisonChainObj(200,100,"x");
ComparisonChainObj var2=new ComparisonChainObj(300,200,"c");
ComparisonChainObj var3=new ComparisonChainObj(300,150,"a");
ComparisonChainObj var4=new ComparisonChainObj(200,150,"d");
ArrayList<ComparisonChainObj> objs = Lists.newArrayList(var1, var2, var3, var4);
Preconditions.checkNotNull(objs);
TreeSet<ComparisonChainObj> comparisonChainObjs = Sets.newTreeSet(objs);
System.out.println(comparisonChainObjs);
}
}
}

还是那句话，不要为了用guava而去用，根据需要来使用吧。