문자를 문자열로 변환하는 방법?

문자를 문자열로 변환하는 방법?

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나는 가지고 char있고 나는 String. 하나에서 다른 것으로 어떻게 변환합니까?

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사용할 수 있습니다 Character.toString(char). 이 메서드는 단순히에 대한 호출을 반환하며이 String.valueOf(char)역시 작동합니다.

다른 사람들이 언급했듯이 문자열 연결은 바로 가기로도 작동합니다.

String s = "" + 's';

그러나 이것은 다음과 같이 요약됩니다.

String s = new StringBuilder().append("").append('s').toString();

때문에 비효율적 인 StringBuildera로 백업 char[](기준 초과 할당 StringBuilder()으로 16) 해당 어레이가 수비를 생성하여 복사 할 String.

String.valueOf(char)char단일 요소 배열 로 래핑 하고 패키지 전용 생성자에 전달 String(char[], boolean)하여 배열 복사를 방지함으로써 "백도어에 들어갑니다" .

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좋은 질문. 다음과 같은 5 가지 6 가지 방법이 있습니다.

1. String stringValueOf = String.valueOf('c'); // most efficient

2. String stringValueOfCharArray = String.valueOf(new char[]{x});

3. String characterToString = Character.toString('c');

4. String characterObjectToString = new Character('c').toString();

   // Although this method seems very simple, 
   // this is less efficient because the concatenation
   // expands to new StringBuilder().append(x).append("").toString();
5. String concatBlankString = 'c' + "";

6. String fromCharArray = new String(new char[]{x});

참고 : Character.toString (char) 은 String.valueOf (char)를 반환합니다 . 그래서 효과적으로 둘 다 동일합니다.

String.valueOf(char[] value)를 호출 new String(char[] value)하여 차례로 valuechar 배열 을 설정합니다 .

public String(char value[]) {
    this.value = Arrays.copyOf(value, value.length);
}

반면에 String.valueOf(char value)다음 패키지 개인 생성자를 호출합니다 .

String(char[] value, boolean share) {
    // assert share : "unshared not supported";
    this.value = value;
}

에서 소스 코드 String.java에서 자바 8 소스 코드

따라서 String.valueOf(char)메모리와 속도 측면 char에서 String.

1. Java에서 기본 문자를 문자열로 변환하는 방법
2. 예제를 사용하여 Java에서 Char를 String으로 변환하는 방법

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다음은 char c를 String으로 변환하는 다양한 방법입니다 (속도 및 효율성 감소 순서).

char c = 'a';
String s = String.valueOf(c);             // fastest + memory efficient
String s = Character.toString(c);
String s = new String(new char[]{c});
String s = String.valueOf(new char[]{c});
String s = new Character(c).toString();
String s = "" + c;                        // slowest + memory inefficient

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다음 중 하나를 사용하십시오.

String str = String.valueOf('c');
String str = Character.toString('c');
String str = 'c' + "";

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다음 Character.toString()과 같은 방법을 사용하십시오 .

char mChar = 'l';
String s = Character.toString(mChar);

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이것을 시도하십시오 : Character.toString(aChar)또는 이것 만 :aChar + ""

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As @WarFox stated - there are 6 methods to convert char to string. However, the fastest one would be via concatenation, despite answers above stating that it is String.valueOf. Here is benchmark that proves that:

@BenchmarkMode(Mode.Throughput)
@Fork(1)
@State(Scope.Thread)
@Warmup(iterations = 10, time = 1, batchSize = 1000, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 10, time = 1, batchSize = 1000, timeUnit = TimeUnit.SECONDS)
public class CharToStringConversion {

    private char c = 'c';

    @Benchmark
    public String stringValueOf() {
        return String.valueOf(c);
    }

    @Benchmark
    public String stringValueOfCharArray() {
        return String.valueOf(new char[]{c});
    }

    @Benchmark
    public String characterToString() {
        return Character.toString(c);
    }

    @Benchmark
    public String characterObjectToString() {
        return new Character(c).toString();
    }

    @Benchmark
    public String concatBlankStringPre() {
        return c + "";
    }

    @Benchmark
    public String concatBlankStringPost() {
        return "" + c;
    }

    @Benchmark
    public String fromCharArray() {
        return new String(new char[]{c});
    }
}

And result:

Benchmark                                        Mode  Cnt       Score      Error  Units
CharToStringConversion.characterObjectToString  thrpt   10   82132.021 ± 6841.497  ops/s
CharToStringConversion.characterToString        thrpt   10  118232.069 ± 8242.847  ops/s
CharToStringConversion.concatBlankStringPost    thrpt   10  136960.733 ± 9779.938  ops/s
CharToStringConversion.concatBlankStringPre     thrpt   10  137244.446 ± 9113.373  ops/s
CharToStringConversion.fromCharArray            thrpt   10   85464.842 ± 3127.211  ops/s
CharToStringConversion.stringValueOf            thrpt   10  119281.976 ± 7053.832  ops/s
CharToStringConversion.stringValueOfCharArray   thrpt   10   86563.837 ± 6436.527  ops/s

As you can see, the fastest one would be c + "" or "" + c;

VM version: JDK 1.8.0_131, VM 25.131-b11

This performance difference is due to -XX:+OptimizeStringConcat optimization. You can read about it here.

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We have various ways to convert a char to String. One way is to make use of static method toString() in Character class:

char ch = 'I'; 
String str1 = Character.toString(ch);

Actually this toString method internally makes use of valueOf method from String class which makes use of char array:

public static String toString(char c) {
    return String.valueOf(c);
}

So second way is to use this directly:

String str2 = String.valueOf(ch);

This valueOf method in String class makes use of char array:

public static String valueOf(char c) {
        char data[] = {c};
        return new String(data, true);
}

So the third way is to make use of an anonymous array to wrap a single character and then passing it to String constructor:

String str4 = new String(new char[]{ch});

The fourth way is to make use of concatenation:

String str3 = "" + ch;

This will actually make use of append method from StringBuilder class which is actually preferred when we are doing concatenation in a loop.

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Here are a few methods, in no particular order:

char c = 'c';

String s = Character.toString(c); // Most efficient way

s = new Character(c).toString(); // Same as above except new Character objects needs to be garbage-collected

s = c + ""; // Least efficient and most memory-inefficient, but common amongst beginners because of its simplicity

s = String.valueOf(c); // Also quite common

s = String.format("%c", c); // Not common

Formatter formatter = new Formatter();
s = formatter.format("%c", c).toString(); // Same as above
formatter.close();

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I am converting Char Array to String

Char[] CharArray={ 'A', 'B', 'C'};
String text = String.copyValueOf(CharArray);

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I've tried the suggestions but ended up implementing it as follows

editView.setFilters(new InputFilter[]{new InputFilter()
        {
            @Override
            public CharSequence filter(CharSequence source, int start, int end,
                                       Spanned dest, int dstart, int dend)
            {
                String prefix = "http://";

                //make sure our prefix is visible
                String destination = dest.toString();

                //Check If we already have our prefix - make sure it doesn't
                //get deleted
                if (destination.startsWith(prefix) && (dstart <= prefix.length() - 1))
                {
                    //Yep - our prefix gets modified - try preventing it.
                    int newEnd = (dend >= prefix.length()) ? dend : prefix.length();

                    SpannableStringBuilder builder = new SpannableStringBuilder(
                            destination.substring(dstart, newEnd));
                    builder.append(source);
                    if (source instanceof Spanned)
                    {
                        TextUtils.copySpansFrom(
                                (Spanned) source, 0, source.length(), null, builder, newEnd);
                    }

                    return builder;
                }
                else
                {
                    //Accept original replacement (by returning null)
                    return null;
                }
            }
        }});

참고URL : https://stackoverflow.com/questions/8172420/how-to-convert-a-char-to-a-string