diff --git a/Java/pom.xml b/Java/pom.xml
index 9930c16..58aa1a7 100644
--- a/Java/pom.xml
+++ b/Java/pom.xml
@@ -4,7 +4,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>org.ciyam</groupId>
 	<artifactId>AT</artifactId>
-	<version>1.3.5</version>
+	<version>1.3.6</version>
 	<packaging>jar</packaging>
 	<properties>
 		<skipTests>true</skipTests>
diff --git a/Java/src/main/java/org/ciyam/at/AtLogger.java b/Java/src/main/java/org/ciyam/at/AtLogger.java
index d8a0f41..0f14085 100644
--- a/Java/src/main/java/org/ciyam/at/AtLogger.java
+++ b/Java/src/main/java/org/ciyam/at/AtLogger.java
@@ -1,11 +1,19 @@
 package org.ciyam.at;
 
+import java.util.function.Supplier;
+
 public interface AtLogger {
 
 	void error(final String message);
 
+	void error(final Supplier<String> messageSupplier);
+
 	void debug(final String message);
 
+	void debug(final Supplier<String> messageSupplier);
+
 	void echo(final String message);
 
+	void echo(final Supplier<String> messageSupplier);
+
 }
diff --git a/Java/src/main/java/org/ciyam/at/FunctionCode.java b/Java/src/main/java/org/ciyam/at/FunctionCode.java
index 56ce9af..33a17e1 100644
--- a/Java/src/main/java/org/ciyam/at/FunctionCode.java
+++ b/Java/src/main/java/org/ciyam/at/FunctionCode.java
@@ -1068,7 +1068,7 @@ public enum FunctionCode {
 		if (functionData.paramCount == 2 && functionData.value2 == null)
 			throw new IllegalFunctionCodeException("Passed value2 is null but function has paramCount of (" + this.paramCount + ")");
 
-		state.getLogger().debug("Function \"" + this.name() + "\"");
+		state.getLogger().debug(() -> String.format("Function \"%s\"", this.name()));
 
 		postCheckExecute(functionData, state, rawFunctionCode);
 	}
diff --git a/Java/src/main/java/org/ciyam/at/MachineState.java b/Java/src/main/java/org/ciyam/at/MachineState.java
index c7fae61..46ee345 100644
--- a/Java/src/main/java/org/ciyam/at/MachineState.java
+++ b/Java/src/main/java/org/ciyam/at/MachineState.java
@@ -675,18 +675,17 @@ public class MachineState {
 
 		// Pre-execution checks
 		if (this.isFinished) {
-			logger.debug("Not executing as already finished!");
+			logger.debug(() -> "Not executing as already finished!");
 			return;
 		}
 
 		if (this.isFrozen && this.currentBalance <= this.frozenBalance) {
-			logger.debug("Not executing as current balance [" + this.currentBalance + "] hasn't increased since being frozen at [" + this.frozenBalance + "]");
+			logger.debug(() -> String.format("Not executing as current balance [%d] hasn't increased since being frozen at [%d]", this.currentBalance, this.frozenBalance));
 			return;
 		}
 
 		if (this.isSleeping && this.sleepUntilHeight != null && this.currentBlockHeight < this.sleepUntilHeight) {
-			logger.debug("Not executing as current block height [" + this.currentBlockHeight + "] hasn't reached sleep-until block height ["
-					+ this.sleepUntilHeight + "]");
+			logger.debug(() -> String.format("Not executing as current block height [%d] hasn't reached sleep-until block height [%d]", this.currentBlockHeight, this.sleepUntilHeight));
 			return;
 		}
 
@@ -716,21 +715,21 @@ public class MachineState {
 				if (nextOpCode == null)
 					throw new IllegalOperationException("OpCode 0x" + String.format("%02x", rawOpCode) + " not recognised");
 
-				this.logger.debug("[PC: " + String.format("%04x", this.programCounter) + "] " + nextOpCode.name());
+				this.logger.debug(() -> String.format("[PC: %04x] %s", this.programCounter, nextOpCode.name()));
 
 				// Request opcode step-fee from API, apply fee to balance, etc.
 				int opcodeSteps = this.api.getOpCodeSteps(nextOpCode);
 				long opcodeFee = opcodeSteps * feePerStep;
 
 				if (this.steps + opcodeSteps > maxSteps) {
-					logger.debug("Enforced sleep due to exceeding maximum number of steps (" + maxSteps + ") per execution round");
+					logger.debug(() -> String.format("Enforced sleep due to exceeding maximum number of steps (%d) per execution round", maxSteps));
 					this.isSleeping = true;
 					break;
 				}
 
 				if (this.currentBalance < opcodeFee) {
 					// Not enough balance left to continue execution - freeze AT
-					logger.debug("Frozen due to lack of balance");
+					logger.debug(() -> "Frozen due to lack of balance");
 					this.isFrozen = true;
 					this.frozenBalance = this.currentBalance;
 					break;
@@ -746,7 +745,7 @@ public class MachineState {
 				// Synchronize programCounter with codeByteBuffer in case of JMPs, branches, etc.
 				this.programCounter = codeByteBuffer.position();
 			} catch (ExecutionException e) {
-				this.logger.debug("Error at PC " + String.format("%04x", this.programCounter) + ": " + e.getMessage());
+				this.logger.error(() -> String.format("Error at PC %04x: %s", this.programCounter, e.getMessage()));
 
 				if (this.onErrorAddress == null) {
 					this.isFinished = true;
@@ -767,18 +766,18 @@ public class MachineState {
 
 		if (this.isSleeping) {
 			if (this.sleepUntilHeight != null)
-				this.logger.debug("Sleeping until block " + this.sleepUntilHeight);
+				this.logger.debug(() -> String.format("Sleeping until block %d", this.sleepUntilHeight));
 			else
-				this.logger.debug("Sleeping until next block");
+				this.logger.debug(() -> "Sleeping until next block");
 		}
 
 		if (this.isStopped) {
-			this.logger.debug("Setting program counter to stop address: " + String.format("%04x", this.onStopAddress));
+			this.logger.debug(() -> String.format("Setting program counter to stop address: %04x", this.onStopAddress));
 			this.programCounter = this.onStopAddress;
 		}
 
 		if (this.isFinished) {
-			this.logger.debug("Finished - refunding remaining funds back to creator");
+			this.logger.debug(() -> "Finished - refunding remaining funds back to creator");
 			this.api.onFinished(this.currentBalance, this);
 			this.currentBalance = 0;
 		}
diff --git a/Java/src/test/java/org/ciyam/at/test/TestLogger.java b/Java/src/test/java/org/ciyam/at/test/TestLogger.java
index 01c624c..80d3082 100644
--- a/Java/src/test/java/org/ciyam/at/test/TestLogger.java
+++ b/Java/src/test/java/org/ciyam/at/test/TestLogger.java
@@ -1,5 +1,7 @@
 package org.ciyam.at.test;
 
+import java.util.function.Supplier;
+
 import org.ciyam.at.AtLogger;
 
 public class TestLogger implements AtLogger {
@@ -9,14 +11,29 @@ public class TestLogger implements AtLogger {
 		System.err.println("ERROR: " + message);
 	}
 
+	@Override
+	public void error(Supplier<String> messageSupplier) {
+		System.err.println("ERROR: " + messageSupplier.get());
+	}
+
 	@Override
 	public void debug(String message) {
 		System.err.println("DEBUG: " + message);
 	}
 
+	@Override
+	public void debug(Supplier<String> messageSupplier) {
+		System.err.println("DEBUG: " + messageSupplier.get());
+	}
+
 	@Override
 	public void echo(String message) {
 		System.err.println("ECHO: " + message);
 	}
 
+	@Override
+	public void echo(Supplier<String> messageSupplier) {
+		System.err.println("ECHO: " + messageSupplier.get());
+	}
+
 }