diff --git a/jadx-core/src/main/java/jadx/core/codegen/InsnGen.java b/jadx-core/src/main/java/jadx/core/codegen/InsnGen.java
index ceb62aa5c..d870cbc52 100644
--- a/jadx-core/src/main/java/jadx/core/codegen/InsnGen.java
+++ b/jadx-core/src/main/java/jadx/core/codegen/InsnGen.java
@@ -215,11 +215,15 @@ public class InsnGen {
 
 			case CHECK_CAST:
 			case CAST:
-				code.add("((");
+				boolean wrap = state.contains(IGState.BODY_ONLY);
+				if (wrap)
+					code.add("(");
+				code.add("(");
 				code.add(useType(((ArgType) ((IndexInsnNode) insn).getIndex())));
-				code.add(") (");
-				code.add(arg(insn.getArg(0), false));
-				code.add("))");
+				code.add(") ");
+				code.add(arg(insn.getArg(0)));
+				if (wrap)
+					code.add(")");
 				break;
 
 			case ARITH:
@@ -564,6 +568,19 @@ public class InsnGen {
 		}
 	}
 
+	private void addArgs(CodeWriter code, InsnNode insn, int k) throws CodegenException {
+		int argsCount = insn.getArgsCount();
+		code.add('(');
+		if (k < argsCount) {
+			code.add(arg(insn.getArg(k), false));
+			for (int i = k + 1; i < argsCount; i++) {
+				code.add(", ");
+				code.add(arg(insn.getArg(i), false));
+			}
+		}
+		code.add(')');
+	}
+
 	private void inlineMethod(MethodNode callMthNode, InvokeNode insn, CodeWriter code) throws CodegenException {
 		IAttribute mia = callMthNode.getAttributes().get(AttributeType.METHOD_INLINE);
 		InsnNode inl = ((MethodInlineAttr) mia).getInsn();
@@ -603,19 +620,6 @@ public class InsnGen {
 		}
 	}
 
-	private void addArgs(CodeWriter code, InsnNode insn, int k) throws CodegenException {
-		int argsCount = insn.getArgsCount();
-		code.add('(');
-		if (k < argsCount) {
-			code.add(arg(insn.getArg(k), false));
-			for (int i = k + 1; i < argsCount; i++) {
-				code.add(", ");
-				code.add(arg(insn.getArg(i), false));
-			}
-		}
-		code.add(')');
-	}
-
 	private void makeArith(ArithNode insn, CodeWriter code, EnumSet<IGState> state) throws CodegenException {
 		ArithOp op = insn.getOp();
 		String v1 = arg(insn.getArg(0));
diff --git a/jadx-core/src/main/java/jadx/core/dex/instructions/args/ArgType.java b/jadx-core/src/main/java/jadx/core/dex/instructions/args/ArgType.java
index bc5e9ce6d..5dfa4bdee 100644
--- a/jadx-core/src/main/java/jadx/core/dex/instructions/args/ArgType.java
+++ b/jadx-core/src/main/java/jadx/core/dex/instructions/args/ArgType.java
@@ -384,6 +384,17 @@ public abstract class ArgType {
 		return null;
 	}
 
+	public static boolean isCastNeeded(ArgType from, ArgType to) {
+		if (from.equals(to)) {
+			return false;
+		}
+		if (from.isObject() && to.isObject()
+				&& clsp.isImplements(from.getObject(), to.getObject())) {
+			return false;
+		}
+		return true;
+	}
+
 	public static ArgType parse(String type) {
 		char f = type.charAt(0);
 		switch (f) {
diff --git a/jadx-core/src/main/java/jadx/core/dex/nodes/ClassNode.java b/jadx-core/src/main/java/jadx/core/dex/nodes/ClassNode.java
index 469c9db51..165f4a15b 100644
--- a/jadx-core/src/main/java/jadx/core/dex/nodes/ClassNode.java
+++ b/jadx-core/src/main/java/jadx/core/dex/nodes/ClassNode.java
@@ -64,9 +64,7 @@ public class ClassNode extends LineAttrNode implements ILoadable {
 				this.interfaces.add(ClassInfo.fromDex(dex, interfaceIdx));
 			}
 
-			if (cls.getClassDataOffset() == 0) {
-				// nothing to loadFile
-			} else {
+			if (cls.getClassDataOffset() != 0) {
 				ClassData clsData = dex.readClassData(cls);
 
 				for (Method mth : clsData.getDirectMethods())
diff --git a/jadx-core/src/main/java/jadx/core/dex/visitors/CodeShrinker.java b/jadx-core/src/main/java/jadx/core/dex/visitors/CodeShrinker.java
index ab159bd56..ff65aad8b 100644
--- a/jadx-core/src/main/java/jadx/core/dex/visitors/CodeShrinker.java
+++ b/jadx-core/src/main/java/jadx/core/dex/visitors/CodeShrinker.java
@@ -10,6 +10,7 @@ import jadx.core.dex.instructions.IfNode;
 import jadx.core.dex.instructions.IndexInsnNode;
 import jadx.core.dex.instructions.InsnType;
 import jadx.core.dex.instructions.InvokeNode;
+import jadx.core.dex.instructions.args.ArgType;
 import jadx.core.dex.instructions.args.FieldArg;
 import jadx.core.dex.instructions.args.InsnArg;
 import jadx.core.dex.instructions.args.InsnWrapArg;
@@ -234,6 +235,17 @@ public class CodeShrinker extends AbstractVisitor {
 				}
 				break;
 
+			case CHECK_CAST:
+				InsnArg castArg = insn.getArg(0);
+				ArgType castType = (ArgType) ((IndexInsnNode)insn).getIndex();
+				if (!ArgType.isCastNeeded(castArg.getType(), castType)) {
+					InsnNode insnNode = new InsnNode(InsnType.MOVE, 1);
+					insnNode.setResult(insn.getResult());
+					insnNode.addArg(castArg);
+					return insnNode;
+				}
+				break;
+
 			default:
 				break;
 		}
diff --git a/jadx-core/src/main/java/jadx/core/dex/visitors/typeresolver/TypeResolver.java b/jadx-core/src/main/java/jadx/core/dex/visitors/typeresolver/TypeResolver.java
index 1c162717f..c3ba1fe39 100644
--- a/jadx-core/src/main/java/jadx/core/dex/visitors/typeresolver/TypeResolver.java
+++ b/jadx-core/src/main/java/jadx/core/dex/visitors/typeresolver/TypeResolver.java
@@ -1,6 +1,8 @@
 package jadx.core.dex.visitors.typeresolver;
 
 import jadx.core.dex.attributes.BlockRegState;
+import jadx.core.dex.instructions.IndexInsnNode;
+import jadx.core.dex.instructions.args.ArgType;
 import jadx.core.dex.instructions.args.InsnArg;
 import jadx.core.dex.instructions.args.RegisterArg;
 import jadx.core.dex.nodes.BlockNode;
@@ -17,6 +19,8 @@ public class TypeResolver extends AbstractVisitor {
 		if (mth.isNoCode())
 			return;
 
+		prepare(mth);
+
 		visitBlocks(mth);
 		visitEdges(mth);
 
@@ -27,6 +31,22 @@ public class TypeResolver extends AbstractVisitor {
 		}
 	}
 
+	/**
+	 * Check argument types (can be broken after merging debug info)
+	 */
+	private void prepare(MethodNode mth) {
+		for (BlockNode block : mth.getBasicBlocks()) {
+			for (InsnNode insn : block.getInstructions()) {
+				switch (insn.getType()) {
+					case CHECK_CAST:
+						ArgType castType = (ArgType) ((IndexInsnNode) insn).getIndex();
+						insn.getResult().getTypedVar().forceSetType(castType);
+						break;
+				}
+			}
+		}
+	}
+
 	private void visitBlocks(MethodNode mth) {
 		for (BlockNode block : mth.getBasicBlocks()) {
 			BlockRegState state = new BlockRegState(mth);
diff --git a/jadx-core/src/test/java/jadx/api/TestDuplicateCast.java b/jadx-core/src/test/java/jadx/api/TestDuplicateCast.java
new file mode 100644
index 000000000..5e34606b0
--- /dev/null
+++ b/jadx-core/src/test/java/jadx/api/TestDuplicateCast.java
@@ -0,0 +1,44 @@
+package jadx.api;
+
+import jadx.core.dex.instructions.InsnType;
+import jadx.core.dex.instructions.args.InsnWrapArg;
+import jadx.core.dex.nodes.ClassNode;
+import jadx.core.dex.nodes.InsnNode;
+import jadx.core.dex.nodes.MethodNode;
+
+import java.util.List;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+public class TestDuplicateCast extends InternalJadxTest {
+
+	public static class TestCls {
+		public int[] method(Object o) {
+			return (int[]) o;
+		}
+	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNode(TestCls.class);
+		MethodNode mth = getMethod(cls, "method");
+
+		List<InsnNode> insns = mth.getBasicBlocks().get(1).getInstructions();
+		assertEquals(insns.size(), 1);
+		InsnNode insnNode = insns.get(0);
+		assertEquals(InsnType.RETURN, insnNode.getType());
+		assertTrue(insnNode.getArg(0).isInsnWrap());
+		InsnNode wrapInsn = ((InsnWrapArg) insnNode.getArg(0)).getWrapInsn();
+		assertEquals(InsnType.CHECK_CAST, wrapInsn.getType());
+		assertFalse(wrapInsn.getArg(0).isInsnWrap());
+
+		String code = cls.getCode().toString();
+		assertThat(code, containsString("return (int[]) o;"));
+	}
+}
diff --git a/jadx-core/src/test/java/jadx/api/TestStringBuilderElimination.java b/jadx-core/src/test/java/jadx/api/TestStringBuilderElimination.java
new file mode 100644
index 000000000..730b71e72
--- /dev/null
+++ b/jadx-core/src/test/java/jadx/api/TestStringBuilderElimination.java
@@ -0,0 +1,31 @@
+package jadx.api;
+
+import jadx.core.dex.nodes.ClassNode;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.not;
+import static org.junit.Assert.assertThat;
+
+public class TestStringBuilderElimination extends InternalJadxTest {
+
+	public static class MyException extends Exception {
+		public MyException(String str, Exception e) {
+//			super("msg:" + str, e);
+		}
+
+		public void method(int k) {
+			System.out.println("k=" + k);
+		}
+	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNode(MyException.class);
+		String code = cls.getCode().toString();
+
+		assertThat(code, not(containsString("new StringBuilder")));
+		assertThat(code, containsString("System.out.println(\"k=\" + k);"));
+	}
+}
diff --git a/jadx-core/src/test/java/jadx/tests/JadxClasspathTest.java b/jadx-core/src/test/java/jadx/tests/JadxClasspathTest.java
new file mode 100644
index 000000000..0392472d2
--- /dev/null
+++ b/jadx-core/src/test/java/jadx/tests/JadxClasspathTest.java
@@ -0,0 +1,41 @@
+package jadx.tests;
+
+import jadx.core.clsp.ClspGraph;
+import jadx.core.dex.instructions.args.ArgType;
+import jadx.core.utils.exceptions.DecodeException;
+
+import java.io.IOException;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static jadx.core.dex.instructions.args.ArgType.object;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class JadxClasspathTest {
+
+	private static final String JAVA_LANG_EXCEPTION = "java.lang.Exception";
+	private static final String JAVA_LANG_THROWABLE = "java.lang.Throwable";
+
+	ClspGraph clsp;
+
+	@Before
+	public void initClsp() throws IOException, DecodeException {
+		clsp = new ClspGraph();
+		clsp.load();
+		ArgType.setClsp(clsp);
+	}
+
+	@Test
+	public void test() {
+		ArgType objExc = object(JAVA_LANG_EXCEPTION);
+		ArgType objThr = object(JAVA_LANG_THROWABLE);
+
+		assertTrue(clsp.isImplements(JAVA_LANG_EXCEPTION, JAVA_LANG_THROWABLE));
+		assertFalse(clsp.isImplements(JAVA_LANG_THROWABLE, JAVA_LANG_EXCEPTION));
+
+		assertFalse(ArgType.isCastNeeded(objExc, objThr));
+		assertTrue(ArgType.isCastNeeded(objThr, objExc));
+	}
+}