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Java - convert PrintStream to String
6 points
In this short article, we would like to show how to convert PrintStream to String in Java.
Quick solution:
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//import java.io.ByteArrayOutputStream;2
//import java.io.PrintStream;3
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try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream();5
PrintStream printStream = new PrintStream(outputStream, true, "UTF-8"))6
{7
printStream.println("First message ...");8
printStream.println("Second message ...");9
printStream.println("Third message ...");10
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String printText = outputStream.toString();12
}
To convert PrintStream to String it is necessary to use some storage to collect PrintStream output data. As that storage ByteArrayOutputStream can be used that creates an in-memory array to keep data, returning them as String on toString() method call. UTF-8 charset allows using a universal encoding that is supported by almost all operating systems and programs.
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package com.examples;2
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import java.io.ByteArrayOutputStream;4
import java.io.IOException;5
import java.io.PrintStream;6
import java.nio.charset.StandardCharsets;7
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public class Program {9
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private static final String UTF8_NAME = StandardCharsets.UTF_8.name();11
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public static void main(String[] args) throws IOException {13
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String printText;15
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try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream();17
PrintStream printStream = new PrintStream(outputStream, true, UTF8_NAME))18
{19
printStream.println("First message ...");20
printStream.println("Second message ...");21
printStream.println("Third message ...");22
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printText = outputStream.toString();24
}25
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System.out.print(printText); // First message ...27
// Second message ...28
// Third message ...29
}30
}Example output:
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First message ...2
Second message ...3
Third message ...
This approach converts ByteArrayOutputStream to byte array that is used to create String with constructor.
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package com.example;2
3
import java.io.ByteArrayOutputStream;4
import java.io.IOException;5
import java.io.PrintStream;6
import java.nio.charset.StandardCharsets;7
8
public class Program {9
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private static final String UTF8_NAME = StandardCharsets.UTF_8.name();11
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public static void main(String[] args) throws IOException {13
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String printText;15
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try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream();17
PrintStream printStream = new PrintStream(outputStream, true, UTF8_NAME))18
{19
printStream.println("First message ...");20
printStream.println("Second message ...");21
printStream.println("Third message ...");22
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printText = new String(outputStream.toByteArray(), UTF8_NAME);24
}25
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System.out.print(printText); // First message ...27
// Second message ...28
// Third message ...29
}30
}Example output:
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First message ...2
Second message ...3
Third message ...This approach uses custom OutputStream implementation to convert written data to String.
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package com.example;2
3
import java.io.IOException;4
import java.io.OutputStream;5
import java.io.PrintStream;6
import java.nio.charset.StandardCharsets;7
8
public class Program {9
10
private static final String UTF8_NAME = StandardCharsets.UTF_8.name();11
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public static void main(String[] args) throws IOException {13
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String printText;15
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try (OutputStream outputStream = new InMemoryOutputStream();17
PrintStream printStream = new PrintStream(outputStream, true, UTF8_NAME))18
{19
printStream.println("First message ...");20
printStream.println("Second message ...");21
printStream.println("Third message ...");22
23
printText = outputStream.toString();24
}25
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System.out.print(printText); // First message ...27
// Second message ...28
// Third message ...29
}30
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private static class InMemoryOutputStream extends OutputStream {32
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private StringBuilder string = new StringBuilder();34
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public void write(int b) throws IOException {37
this.string.append((char) b );38
}39
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public String toString() {41
return this.string.toString();42
}43
}44
}
