diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/impl/charset/UTF16Charset.java b/teavm-classlib/src/main/java/org/teavm/classlib/impl/charset/UTF16Charset.java
deleted file mode 100644
index 8bf3d0d44..000000000
--- a/teavm-classlib/src/main/java/org/teavm/classlib/impl/charset/UTF16Charset.java
+++ /dev/null
@@ -1,10 +0,0 @@
-package org.teavm.classlib.impl.charset;
-
-/**
- *
- * @author Alexey Andreev
- */
-@CharsetName("UTF-16")
-public class UTF16Charset {
-
-}
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/impl/charset/UTF16Helper.java b/teavm-classlib/src/main/java/org/teavm/classlib/impl/charset/UTF16Helper.java
new file mode 100644
index 000000000..9396db9da
--- /dev/null
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/impl/charset/UTF16Helper.java
@@ -0,0 +1,39 @@
+package org.teavm.classlib.impl.charset;
+
+/**
+ *
+ * @author Alexey Andreev
+ */
+public class UTF16Helper {
+    public static final int SURROGATE_BIT_MASK = 0xFC00;
+    public static final int SURROGATE_BIT_INV_MASK = 0x03FF;
+    public static final int HIGH_SURROGATE_BITS = 0xF800;
+    public static final int LOW_SURROGATE_BITS = 0xF800;
+    public static final int MEANINGFUL_SURROGATE_BITS = 10;
+    public static final int SUPPLEMENTARY_PLANE = 0x10000;
+
+    public static char highSurrogate(int codePoint) {
+        return (char)(HIGH_SURROGATE_BITS | (codePoint >> MEANINGFUL_SURROGATE_BITS) & SURROGATE_BIT_INV_MASK);
+    }
+
+    public static char lowSurrogate(int codePoint) {
+        return (char)(HIGH_SURROGATE_BITS | codePoint & SURROGATE_BIT_INV_MASK);
+    }
+
+    public static boolean isHighSurrogate(char c) {
+        return (c & SURROGATE_BIT_MASK) == HIGH_SURROGATE_BITS;
+    }
+
+    public static boolean isLowSurrogate(char c) {
+        return (c & SURROGATE_BIT_MASK) == LOW_SURROGATE_BITS;
+    }
+
+    public static boolean isSurrogatePair(char a, char b) {
+        return isHighSurrogate(a) && isLowSurrogate(b);
+    }
+
+    public static int buildCodePoint(char a, char b) {
+        return ((a & SURROGATE_BIT_INV_MASK) << MEANINGFUL_SURROGATE_BITS) |
+            (b & SURROGATE_BIT_INV_MASK) + SUPPLEMENTARY_PLANE;
+    }
+}
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
index a8e143a4d..775937ecb 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
@@ -1,5 +1,6 @@
 package org.teavm.classlib.java.lang;
 
+import org.teavm.classlib.impl.charset.UTF16Helper;
 import org.teavm.classlib.java.lang.io.TSerializable;
 import org.teavm.classlib.java.util.TArrays;
 import org.teavm.javascript.ni.Remove;
@@ -289,13 +290,13 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
     }
 
     protected TAbstractStringBuilder appendCodePoint(int codePoint) {
-        if (codePoint < TString.SUPPLEMENTARY_PLANE) {
+        if (codePoint < UTF16Helper.SUPPLEMENTARY_PLANE) {
             return append((char)codePoint);
         }
         ensureCapacity(length + 2);
-        codePoint -= TString.SUPPLEMENTARY_PLANE;
-        buffer[length++] = TString.highSurrogate(codePoint);
-        buffer[length++] = TString.lowSurrogate(codePoint);
+        codePoint -= UTF16Helper.SUPPLEMENTARY_PLANE;
+        buffer[length++] = UTF16Helper.highSurrogate(codePoint);
+        buffer[length++] = UTF16Helper.lowSurrogate(codePoint);
         return this;
     }
 
@@ -362,6 +363,6 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
     }
 
     public void setLength(int newLength) {
-        length = 0;
+        length = newLength;
     }
 }
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
index af5ab3ae9..fb35e560d 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
@@ -1,5 +1,6 @@
 package org.teavm.classlib.java.lang;
 
+import org.teavm.classlib.impl.charset.UTF16Helper;
 import org.teavm.classlib.java.lang.io.TSerializable;
 import org.teavm.javascript.ni.GeneratedBy;
 import org.teavm.javascript.ni.Rename;
@@ -10,12 +11,6 @@ import org.teavm.javascript.ni.Rename;
  */
 public class TString extends TObject implements TSerializable, TComparable<TString>,
         TCharSequence {
-    static int SURROGATE_BIT_MASK = 0xFC00;
-    static int SURROGATE_BIT_INV_MASK = 0x03FF;
-    static int HIGH_SURROGATE_BITS = 0xF800;
-    static int LOW_SURROGATE_BITS = 0xF800;
-    static int MEANINGFUL_SURROGATE_BITS = 10;
-    static int SUPPLEMENTARY_PLANE = 0x10000;
     private char[] characters;
     private transient int hashCode;
 
@@ -54,29 +49,26 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
     }
 
     public int codePointAt(int index) {
-        if (index == characters.length - 1 || (characters[index] & SURROGATE_BIT_MASK) != HIGH_SURROGATE_BITS ||
-                (characters[index + 1] & SURROGATE_BIT_MASK) != LOW_SURROGATE_BITS) {
+        if (index == characters.length - 1 || !UTF16Helper.isHighSurrogate(characters[index]) ||
+                !UTF16Helper.isLowSurrogate(characters[index + 1])) {
             return characters[index];
         }
-        return ((characters[index] & SURROGATE_BIT_INV_MASK) << MEANINGFUL_SURROGATE_BITS) |
-                (characters[index + 1] & SURROGATE_BIT_INV_MASK) + SUPPLEMENTARY_PLANE;
+        return UTF16Helper.buildCodePoint(characters[index], characters[index + 1]);
     }
 
     public int codePointBefore(int index) {
-        if (index == 1 || (characters[index] & SURROGATE_BIT_MASK) != LOW_SURROGATE_BITS ||
-                (characters[index - 1] & SURROGATE_BIT_MASK) != HIGH_SURROGATE_BITS) {
+        if (index == 1 || !UTF16Helper.isHighSurrogate(characters[index]) ||
+                UTF16Helper.isLowSurrogate(characters[index - 1])) {
             return characters[index - 1];
         }
-        return ((characters[index - 1] & SURROGATE_BIT_INV_MASK) << MEANINGFUL_SURROGATE_BITS) |
-                (characters[index] & SURROGATE_BIT_INV_MASK) + SUPPLEMENTARY_PLANE;
+        return UTF16Helper.buildCodePoint(characters[index - 1], characters[index]);
     }
 
     public int codePointCount(int beginIndex, int endIndex) {
         int count = endIndex;
         --endIndex;
         for (int i = beginIndex; i < endIndex; ++i) {
-            if ((characters[i] & SURROGATE_BIT_MASK) == HIGH_SURROGATE_BITS &&
-                    (characters[i + 1] & SURROGATE_BIT_MASK) == LOW_SURROGATE_BITS) {
+            if (UTF16Helper.isHighSurrogate(characters[i]) && UTF16Helper.isLowSurrogate(characters[i + 1])) {
                 --count;
             }
         }
@@ -85,8 +77,8 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
 
     public int offsetByCodePoints(int index, int codePointOffset) {
         for (int i = 0; i < codePointOffset; ++i) {
-            if (index < characters.length - 1 && (characters[index] & SURROGATE_BIT_MASK) == HIGH_SURROGATE_BITS &&
-                    (characters[index + 1] & SURROGATE_BIT_MASK) == LOW_SURROGATE_BITS) {
+            if (index < characters.length - 1 && UTF16Helper.isHighSurrogate(characters[index]) &&
+                    UTF16Helper.isLowSurrogate(characters[index + 1])) {
                 index += 2;
             } else {
                 index++;
@@ -192,17 +184,8 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
         return true;
     }
 
-    static char highSurrogate(int codePoint) {
-        return (char)(TString.HIGH_SURROGATE_BITS | (codePoint >> TString.MEANINGFUL_SURROGATE_BITS) &
-                TString.SURROGATE_BIT_INV_MASK);
-    }
-
-    static char lowSurrogate(int codePoint) {
-        return (char)(TString.HIGH_SURROGATE_BITS | codePoint & TString.SURROGATE_BIT_INV_MASK);
-    }
-
     public int indexOf(int ch, int fromIndex) {
-        if (ch < SUPPLEMENTARY_PLANE) {
+        if (ch < UTF16Helper.SUPPLEMENTARY_PLANE) {
             char bmpChar = (char)ch;
             for (int i = fromIndex; i < characters.length; ++i) {
                 if (characters[i] == bmpChar) {
@@ -211,8 +194,8 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
             }
             return -1;
         } else {
-            char hi = highSurrogate(ch);
-            char lo = lowSurrogate(ch);
+            char hi = UTF16Helper.highSurrogate(ch);
+            char lo = UTF16Helper.lowSurrogate(ch);
             for (int i = fromIndex; i < characters.length - 1; ++i) {
                 if (characters[i] == hi && characters[i + 1] == lo) {
                     return i;
@@ -227,7 +210,7 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
     }
 
     public int lastIndexOf(int ch, int fromIndex) {
-        if (ch < SUPPLEMENTARY_PLANE) {
+        if (ch < UTF16Helper.SUPPLEMENTARY_PLANE) {
             char bmpChar = (char)ch;
             for (int i = fromIndex; i >= 0; --i) {
                 if (characters[i] == bmpChar) {
@@ -236,8 +219,8 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
             }
             return -1;
         } else {
-            char hi = highSurrogate(ch);
-            char lo = lowSurrogate(ch);
+            char hi = UTF16Helper.highSurrogate(ch);
+            char lo = UTF16Helper.lowSurrogate(ch);
             for (int i = fromIndex; i >= 1; --i) {
                 if (characters[i] == lo && characters[i - 1] == hi) {
                     return i;
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/io/TPrintStream.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/io/TPrintStream.java
index 69ad1feb7..48bcd7d30 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/io/TPrintStream.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/io/TPrintStream.java
@@ -1,5 +1,6 @@
 package org.teavm.classlib.java.lang.io;
 
+import org.teavm.classlib.java.lang.TMath;
 import org.teavm.classlib.java.lang.TStringBuilder;
 
 /**
@@ -95,7 +96,16 @@ public class TPrintStream extends TFilterOutputStream {
     }
 
     public void print(char[] s) {
+        print(s, 0, s.length);
+    }
 
+    private void print(char[] s, int begin, int end) {
+        int[] codePoints = new int[TMath.min(s.length, 4096)];
+    }
+
+    public void print(char c) {
+        buffer[0] = c;
+        print(buffer, 0, 1);
     }
 
     public void print(int i) {