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com.google.common.base.Strings

Guava Java

Guavacom.google.common.base.Stringsの利用サンプルです。
Stringsクラスは文字列に関するユーティリティメソッドを提供してくれます。

サンプルコードで試したのは以下の通りです。


指定回数繰り返した文字列を取得

■API

  • Strings#repeat

■サンプル

System.out.println("## Strings.repeat execute");
System.out.println(Strings.repeat("a", 10));
System.out.println(Strings.repeat("hello", 3));

■実行結果

## Strings.repeat execute
aaaaaaaaaa
hellohellohello


Left Pad

■API

  • Strings#padStart

■サンプル

System.out.println("## Strings.padStart execute");
System.out.println(Strings.padStart("123", 5, '0'));
System.out.println(Strings.padStart("abcde", 3, '*'));

■実行結果

## Strings.padStart execute
00123
abcde


Right Pad

■API

  • Strings#padEnd

■サンプル

System.out.println("## Strings.padEnd execute");
System.out.println(Strings.padEnd("123.1", 7, '0'));
System.out.println(Strings.padEnd("abcde", 3, '*'));

■実行結果

## Strings.padEnd execute
123.100
abcde


指定文字列が空またはnullかどうかをチェック

■API

  • Strings#isNullOrEmpty

■サンプル

System.out.println("## Strings.isNullOrEmpty execute");
System.out.println("null = " + Strings.isNullOrEmpty(null));
System.out.println("empty string = " + Strings.isNullOrEmpty(""));
System.out.println("hello = " + Strings.isNullOrEmpty("hello"));

■実行結果

## Strings.isNullOrEmpty execute
null = true
empty string = true
hello = false


nullを空文字列にする

■API

  • Strings#nullToEmpty

■サンプル

System.out.println("## Strings.nullToEmpty execute");
System.out.println("null -> [" + Strings.nullToEmpty(null) + "]");
System.out.println("hello -> [" + Strings.nullToEmpty("hello") + "]");

■実行結果

## Strings.nullToEmpty execute
null -> []
hello -> [hello]


空文字列をnullにする

■API

  • Strings#emptyToNull

■サンプル

System.out.println("## Strings.emptyToNull execute");
System.out.println("empty string -> [" + Strings.emptyToNull("") + "]");
System.out.println("hello -> [" + Strings.emptyToNull("hello") + "]");

■実行結果

## Strings.emptyToNull execute
empty string -> [null]
hello -> [hello]


2つの文字列の共通のprefix取得

■API

  • Strings#commonPrefix

■サンプル

System.out.println("## Strings.commonPrefix execute");
System.out.println("foo_123456.txt & foo_234567.txt common prefix is [" + Strings.commonPrefix("foo_123456.txt", "foo_234567.txt") + "]");
System.out.println("20130429 & 20130430 common prefix is [" + Strings.commonPrefix("20130429", "20130430") + "]");
System.out.println("abc & def common prefix is [" + Strings.commonPrefix("abc", "def") + "]");

■実行結果

## Strings.commonPrefix execute
foo_123456.txt & foo_234567.txt common prefix is [foo_]
20130429 & 20130430 common prefix is [201304]
abc & def common prefix is []


2つの文字列の共通のsuffix取得

■API

  • Strings#commonSuffix

■サンプル

System.out.println("## Strings.commonSuffix execute");
System.out.println("foo_123456.txt & foo_234567.txt common suffix is [" + Strings.commonSuffix("foo_123456.txt", "foo_234567.txt") + "]");
System.out.println("20130429 & 20120429 common suffix is [" + Strings.commonSuffix("20130429", "20120429") + "]");
System.out.println("abc & def common suffix is [" + Strings.commonSuffix("abc", "def") + "]");

■実行結果

## Strings.commonSuffix execute
foo_123456.txt & foo_234567.txt common suffix is [.txt]
20130429 & 20120429 common suffix is [0429]
abc & def common suffix is []




試したソースコードの全体は以下です。

import com.google.common.base.Strings;


public class StringsTrial {

    public static void main(String[] args) {

        // 指定の文字列を指定回数繰り返す
        System.out.println("## Strings.repeat execute");
        System.out.println(Strings.repeat("a", 10));
        System.out.println(Strings.repeat("hello", 3));

        // 文字列の先頭を指定文字で埋める(left pad)
        System.out.println("## Strings.padStart execute");
        System.out.println(Strings.padStart("123", 5, '0'));
        System.out.println(Strings.padStart("abcde", 3, '*'));

        // 文字列の末尾を指定文字で埋める(right pad)
        System.out.println("## Strings.padEnd execute");
        System.out.println(Strings.padEnd("123.1", 7, '0'));
        System.out.println(Strings.padEnd("abcde", 3, '*'));

        // nullまたは空文字列(length == 0)かどうかをチェックする
        System.out.println("## Strings.isNullOrEmpty execute");
        System.out.println("null = " + Strings.isNullOrEmpty(null));
        System.out.println("empty string = " + Strings.isNullOrEmpty(""));
        System.out.println("hello = " + Strings.isNullOrEmpty("hello"));

        // nullの場合空文字列を返す
        System.out.println("## Strings.nullToEmpty execute");
        System.out.println("null -> [" + Strings.nullToEmpty(null) + "]");
        System.out.println("hello -> [" + Strings.nullToEmpty("hello") + "]");

        // 空文字列の場合nullを返す
        System.out.println("## Strings.emptyToNull execute");
        System.out.println("empty string -> [" + Strings.emptyToNull("") + "]");
        System.out.println("hello -> [" + Strings.emptyToNull("hello") + "]");

        // 指定文字列同士の共通のprefixを返す
        System.out.println("## Strings.commonPrefix execute");
        System.out.println("foo_123456.txt & foo_234567.txt common prefix is [" + Strings.commonPrefix("foo_123456.txt", "foo_234567.txt") + "]");
        System.out.println("20130429 & 20130430 common prefix is [" + Strings.commonPrefix("20130429", "20130430") + "]");
        System.out.println("abc & def common prefix is [" + Strings.commonPrefix("abc", "def") + "]");

        // 指定文字列同士の共通のsuffixを返す
        System.out.println("## Strings.commonSuffix execute");
        System.out.println("foo_123456.txt & foo_234567.txt common suffix is [" + Strings.commonSuffix("foo_123456.txt", "foo_234567.txt") + "]");
        System.out.println("20130429 & 20120429 common suffix is [" + Strings.commonSuffix("20130429", "20120429") + "]");
        System.out.println("abc & def common suffix is [" + Strings.commonSuffix("abc", "def") + "]");
    }

}