Guava入门第五章(Strings)

Strings详细介绍

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package com.lvshihao.guava;

import com.google.common.base.CharMatcher;
import com.google.common.base.Charsets;
import com.google.common.base.Strings;
import org.junit.Test;

import java.nio.charset.Charset;

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

/**
 *@author: LVSHIHAO
 *@description: GUAVA Strings detailed introduction
 */
public class StringsTest {

    @Test
    public void testGuavaStringsMethod(){
        /**
         * emptyToNull() if incoming String is it Empty , is Empty Then just return null
         */
        assertThat(Strings.emptyToNull(""),nullValue());
        /**
         * nullToEmpty() if incoming String is it null , is null Then just return ""
         */
        assertThat(Strings.nullToEmpty(null),equalTo(""));
        /**
         * commonPrefix() compare two String Common characters for prefix conduct return
         */
        assertThat(Strings.commonPrefix("lvshihao","lvxu"),equalTo("lv"));
        /**
         * commonSuffix() compare two String Common characters for suffix conduct return
         */
        assertThat(Strings.commonSuffix("lvshihao","hello"),equalTo("o"));
        /**
         * isNullOrEmpty() if incoming args is null or "" but return true
         */
        assertThat(Strings.isNullOrEmpty(null),equalTo(true));
        assertThat(Strings.isNullOrEmpty(""),equalTo(true));
        /**
         * repeat() repeat append this String several times
         */
        assertThat(Strings.repeat("lvshihao",2),equalTo("lvshihaolvshihao"));
        /**
         * padStart() String length less that minLength but prefix append Less n characters
         */
        assertThat(Strings.padStart("lvshihao",10,'6'),equalTo("66lvshihao"));
        /**
         * padEnd()  String length less that minLength but suffix append Less n characters
         */
        assertThat(Strings.padEnd("lvshihao",10,'6'),equalTo("lvshihao66"));
    }

    @Test
    public void testGuavaCharsetsMethod(){
        /**
         * Charsets Encoding constants can be obtained through Charsets
         */
        Charset charset = Charset.forName("UTF-8");
        assertThat(Charsets.UTF_8,equalTo(charset));
    }

    @Test
    public void testCharMatcher(){
        /**
         * CharMatcher.javaDigit().matches()
         * Through this method, you can match whether the character is a number, and return true if it is
         */
        assertThat(CharMatcher.javaDigit().matches('5'),equalTo(true));

        /**
         * CharMatcher.is().countIn()
         * Through this method, you can check how many times this character appears in the string
         */
        assertThat(CharMatcher.is('A').countIn("Alex the Google Guava to Us"),equalTo(1));

        /**
         * CharMatcher.breakingWhitespace().collapseFrom()
         * Replace spaces with specified characters
         */
        assertThat(CharMatcher.breakingWhitespace().collapseFrom("       hello lvshihao",' '),equalTo(" hello lvshihao"));

        /**
         * .digit().or(CharMatcher.whitespace()).removeFrom()
         * remove number And Spaces In The String
         */
        assertThat(CharMatcher.digit().or(CharMatcher.whitespace()).removeFrom("hello 234 world "),equalTo("helloworld"));

        /**
         * .digit().or(CharMatcher.whitespace()).removeFrom()
         * retain number And Spaces In The String
         */
        assertThat(CharMatcher.digit().or(CharMatcher.whitespace()).retainFrom("hello 234 world "),equalTo(" 234  "));

    }
}