First test version

pom.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>fsmpi.gaming.tnt-crusher</groupId>
+    <artifactId>tnt-crusher</artifactId>
+    <version>1.0-SNAPSHOT</version>
+  <packaging>jar</packaging>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+    </properties>
+
+    <build>
+        <sourceDirectory>${project.basedir}/src/main/java</sourceDirectory>
+        <resources>
+            <resource>
+                <directory>${project.basedir}/src/main/resources</directory>
+                <includes>
+                <include>plugin.yml</include>
+                </includes>
+            </resource>
+        </resources>
+    </build>
+
+    <repositories>
+        <repository>
+            <id>spigot-repo</id>
+            <url>https://hub.spigotmc.org/nexus/content/repositories/snapshots/</url>
+        </repository>
+    </repositories>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.spigotmc</groupId>
+            <artifactId>spigot-api</artifactId>
+            <version>1.20.4-R0.1-SNAPSHOT</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+</project>

src/main/java/fsmpi/gaming/tnt_crusher/BlockModifier.java

+package fsmpi.gaming.tnt_crusher;
+
+import org.bukkit.block.Block;
+
+public interface BlockModifier {
+    public void modify(Block block);
+}

src/main/java/fsmpi/gaming/tnt_crusher/ChangeBlockModifier.java

+package fsmpi.gaming.tnt_crusher;
+
+import java.util.Random;
+
+import org.bukkit.Material;
+import org.bukkit.block.Block;
+
+public class ChangeBlockModifier implements BlockModifier {
+    public Material checkFor;
+    public Material changeTo;
+    public float modifierChance;
+
+    public ChangeBlockModifier(Material checkFor, Material changeTo, float modifierChance) {
+        this.checkFor = checkFor;
+        this.changeTo = changeTo;
+        this.modifierChance = modifierChance;
+    }
+    @Override
+    public void modify(Block block) {
+        if (block.getType() == checkFor) {
+            Random r = new Random();
+            if (r.nextFloat() < modifierChance) {
+                block.setType(changeTo);
+            }
+        }
+    }
+    
+}

src/main/java/fsmpi/gaming/tnt_crusher/ExplosionBlockHandler.java

+package fsmpi.gaming.tnt_crusher;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+
+import org.bukkit.Location;
+import org.bukkit.block.Block;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.block.BlockExplodeEvent;
+import org.bukkit.event.entity.EntityExplodeEvent;
+
+public class ExplosionBlockHandler implements Listener {
+
+    private ArrayList<BlockModifier> modifiers;
+
+    public ExplosionBlockHandler(List<BlockModifier> modifiers) {
+        this.modifiers = new ArrayList<>(modifiers);
+    }
+    
+    @EventHandler
+    public void onEntityExplode(EntityExplodeEvent event) {
+        handleExplosion(event.getLocation(), event.blockList());
+    }
+    @EventHandler
+    public void onBlockExplode(BlockExplodeEvent event) {
+        handleExplosion(event.getBlock().getLocation(), event.blockList());
+    }
+    public void handleExplosion(Location location, List<Block> blockList) {
+        HashMap<Location, Block> blockMap = getBlockMap(blockList);
+
+        Collection<Block> targetBlocks = getTargetBlockList(location, blockMap);
+
+        modifyBlocks(targetBlocks);
+    }
+
+    private HashMap<Location, Block> getBlockMap(List<Block> blockList) {
+        HashMap<Location, Block> blockMap = new HashMap<>();
+        for (Block block : blockList) {
+            blockMap.put(block.getLocation(), block);
+        }
+        return blockMap;
+    }
+
+    private Collection<Block> getTargetBlockList(Location center, HashMap<Location, Block> explosionMap) {
+        HashMap<Location, Block> targetMap = new HashMap<>();
+        for (Location location : explosionMap.keySet()) {
+            checkLocation(location.clone().add(1, 0, 0), explosionMap, targetMap);
+            checkLocation(location.clone().add(-1, 0, 0), explosionMap, targetMap);
+            checkLocation(location.clone().add(0, 1, 0), explosionMap, targetMap);
+            checkLocation(location.clone().add(0, -1, 0), explosionMap, targetMap);
+            checkLocation(location.clone().add(0, 0, 1), explosionMap, targetMap);
+            checkLocation(location.clone().add(0, 0, -1), explosionMap, targetMap);
+        }
+        return targetMap.values();
+    }
+    
+    private void checkLocation(Location location, HashMap<Location, Block> explosionMap, HashMap<Location, Block> targetMap) {
+        if (isTargetLocation(location, explosionMap, targetMap)) {
+            targetMap.put(location, location.getBlock());
+        }
+    }
+    private boolean isTargetLocation(Location location, HashMap<Location, Block> explosionMap, HashMap<Location, Block> targetMap) {
+        return !explosionMap.containsKey(location) && !targetMap.containsKey(location);
+    }
+
+    private void modifyBlocks(Collection<Block> blocks) {
+        for (Block block : blocks) {
+            for (BlockModifier blockModifier : modifiers) {
+                blockModifier.modify(block);
+            }
+        }
+    }
+
+    public void addBlockModifier(BlockModifier blockModifier) {
+        modifiers.add(blockModifier);
+    }
+    public void removeBlockModifier(BlockModifier blockModifier) {
+        modifiers.remove(blockModifier);
+    }
+    public List<BlockModifier> getBlockModifierList() {
+        return modifiers.subList(0, modifiers.size() - 1);
+    }
+}

src/main/java/fsmpi/gaming/tnt_crusher/MyPlugin.java

+package fsmpi.gaming.tnt_crusher;
+
+import java.util.ArrayList;
+
+import org.bukkit.Material;
+import org.bukkit.plugin.java.JavaPlugin;
+
+public class MyPlugin extends JavaPlugin {
+    
+    @Override
+    public void onEnable() {
+        ArrayList<BlockModifier> modifiers = new ArrayList<>();
+        modifiers.add(new ChangeBlockModifier(Material.COBBLESTONE, Material.DIAMOND_BLOCK, 1));
+        getServer().getPluginManager().registerEvents(new ExplosionBlockHandler(modifiers), this);
+    }
+
+    @Override
+    public void onDisable() {
+        
+    }
+}

src/main/resources/plugin.yml

+name: TNT-Crusher
+main: fsmpi.gaming.tnt_crusher.MyPlugin
+version: ${project.version}
+api-version: 1.20
+commands: