Replace StringBuilder append chain with strings concatenation

src/main/java/jadx/Consts.java

@@ -13,5 +13,7 @@ public class Consts {
 	public static final String CLASS_THROWABLE = "java.lang.Throwable";
 	public static final String CLASS_ENUM = "java.lang.Enum";
 
+	public static final String CLASS_STRING_BUILDER = "java.lang.StringBuilder";
+
 	public static final String DALVIK_SIGNATURE = "dalvik.annotation.Signature";
 }

src/main/java/jadx/codegen/InsnGen.java

@@ -32,6 +32,7 @@ import jadx.utils.exceptions.CodegenException;
 import java.util.ArrayList;
 import java.util.EnumSet;
 import java.util.HashMap;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -213,7 +214,7 @@ public class InsnGen {
 
 			case RETURN:
 				if (insn.getArgsCount() != 0)
-					code.add("return " + arg(insn.getArg(0)));
+					code.add("return ").add(arg(insn.getArg(0)));
 				else
 					code.add("return");
 				break;
@@ -227,7 +228,7 @@ public class InsnGen {
 				break;
 
 			case THROW:
-				code.add("throw " + arg(insn.getArg(0)));
+				code.add("throw ").add(arg(insn.getArg(0)));
 				break;
 
 			case CMP_L:
@@ -281,7 +282,7 @@ public class InsnGen {
 				code.add(ifield((IndexInsnNode) insn, 0));
 				break;
 			case IPUT:
-				code.add(ifield((IndexInsnNode) insn, 1) + " = " + arg(insn.getArg(0)));
+				code.add(ifield((IndexInsnNode) insn, 1)).add(" = ").add(arg(insn.getArg(0)));
 				break;
 
 			case SGET:
@@ -290,7 +291,18 @@ public class InsnGen {
 			case SPUT:
 				IndexInsnNode node = (IndexInsnNode) insn;
 				fieldPut(node);
-				code.add(sfield(node) + " = " + arg(node.getArg(0)));
+				code.add(sfield(node)).add(" = ").add(arg(node.getArg(0)));
+				break;
+
+			case STR_CONCAT:
+				// TODO: wrap in braces only if necessary
+				code.add('(');
+				for (Iterator<InsnArg> it = insn.getArguments().iterator(); it.hasNext(); ) {
+					code.add(arg(it.next()));
+					if (it.hasNext())
+						code.add(" + ");
+				}
+				code.add(')');
 				break;
 
 			case MONITOR_ENTER:

src/main/java/jadx/dex/info/MethodInfo.java

@@ -49,6 +49,10 @@ public final class MethodInfo {
 		return declClass.getFullName() + "." + name;
 	}
 
+
+	public String getFullId() {
+		return declClass.getFullName() + "." + shortId;
+	}
 	/**
 	 * Method name and signature
 	 */

src/main/java/jadx/dex/instructions/InsnType.java

@@ -51,6 +51,8 @@ public enum InsnType {
 	BREAK,
 	CONTINUE,
 
+	STR_CONCAT, // strings concatenation
+
 	TERNARY,
 	ARGS, // just generate arguments
 

src/main/java/jadx/dex/nodes/MethodNode.java

@@ -65,12 +65,12 @@ public class MethodNode extends AttrNode implements ILoadable {
 	private IContainer region;
 	private List<ExceptionHandler> exceptionHandlers;
 
-	public MethodNode(ClassNode classNode, Method mth) {
-		this.mthInfo = MethodInfo.fromDex(classNode.dex(), mth.getMethodIndex());
+	public MethodNode(ClassNode classNode, Method mthData) {
+		this.mthInfo = MethodInfo.fromDex(classNode.dex(), mthData.getMethodIndex());
 		this.parentClass = classNode;
-		this.accFlags = new AccessInfo(mth.getAccessFlags(), AFType.METHOD);
-		this.methodData = mth;
-		this.noCode = (methodData.getCodeOffset() == 0);
+		this.accFlags = new AccessInfo(mthData.getAccessFlags(), AFType.METHOD);
+		this.noCode = (mthData.getCodeOffset() == 0);
+		this.methodData = (noCode ? null : mthData);
 	}
 
 	@Override

src/main/java/jadx/dex/visitors/CodeShrinker.java

 package jadx.dex.visitors;
 
+import jadx.Consts;
 import jadx.dex.attributes.AttributeFlag;
+import jadx.dex.info.MethodInfo;
 import jadx.dex.instructions.ArithNode;
 import jadx.dex.instructions.ArithOp;
 import jadx.dex.instructions.IfNode;
 import jadx.dex.instructions.InsnType;
+import jadx.dex.instructions.InvokeNode;
 import jadx.dex.instructions.args.InsnArg;
 import jadx.dex.instructions.args.InsnWrapArg;
 import jadx.dex.instructions.args.LiteralArg;
 import jadx.dex.instructions.args.RegisterArg;
+import jadx.dex.instructions.mods.ConstructorInsn;
 import jadx.dex.nodes.BlockNode;
 import jadx.dex.nodes.InsnNode;
 import jadx.dex.nodes.MethodNode;
@@ -16,6 +20,7 @@ import jadx.utils.BlockUtils;
 import jadx.utils.exceptions.JadxRuntimeException;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.slf4j.Logger;
@@ -154,12 +159,49 @@ public class CodeShrinker extends AbstractVisitor {
 				}
 				break;
 
+			case INVOKE:
+				MethodInfo callMth = ((InvokeNode) insn).getCallMth();
+				if (callMth.getDeclClass().getFullName().equals(Consts.CLASS_STRING_BUILDER)
+						&& callMth.getShortId().equals("toString()")
+						&& insn.getArg(0).isInsnWrap()) {
+					List<InsnNode> chain = flattenInsnChain(insn);
+					if (chain.size() > 1 && chain.get(0).getType() == InsnType.CONSTRUCTOR) {
+						ConstructorInsn constr = (ConstructorInsn) chain.get(0);
+						if (constr.getClassType().getFullName().equals(Consts.CLASS_STRING_BUILDER)
+								&& constr.getArgsCount() == 0) {
+							int len = chain.size();
+							InsnNode concatInsn = new InsnNode(InsnType.STR_CONCAT, len - 1);
+							for (int i = 1; i < len; i++) {
+								concatInsn.addArg(chain.get(i).getArg(1));
+							}
+							concatInsn.setResult(insn.getResult());
+							return concatInsn;
+						}
+					}
+				}
+				break;
+
 			default:
 				break;
 		}
 		return null;
 	}
 
+	private static List<InsnNode> flattenInsnChain(InsnNode insn) {
+		List<InsnNode> chain = new ArrayList<InsnNode>();
+		InsnArg i = insn.getArg(0);
+		while (i.isInsnWrap()) {
+			InsnNode wrapInsn = ((InsnWrapArg) i).getWrapInsn();
+			chain.add(wrapInsn);
+			if(wrapInsn.getArgsCount() == 0)
+				break;
+
+			i = wrapInsn.getArg(0);
+		}
+		Collections.reverse(chain);
+		return chain;
+	}
+
 	public static InsnArg inlineArgument(MethodNode mth, RegisterArg arg) {
 		InsnNode assignInsn = arg.getAssignInsn();
 		if (assignInsn == null)