fmt

Author: Kuangcp

class/src/test/java/syntax/tryblock/FinallyTest.java

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+package syntax.tryblock;
+
+import org.junit.Test;
+
+/**
+ * @author Kuangcp
+ * 2025-03-12 18:22
+ */
+public class FinallyTest {
+
+
+    /**
+     * 将 输出 try 和 finally
+     */
+    @Test
+    public void testExceptionFinally() throws Exception {
+        try {
+            System.out.println("try");
+            throw new RuntimeException("error");
+        } finally {
+            System.out.println("finally");
+        }
+    }
+}

class/src/test/java/syntax/tryblock/FinallyWithReturn.java

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+package syntax.tryblock;
+
+import lombok.extern.slf4j.Slf4j;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.concurrent.ThreadLocalRandom;
+
+/**
+ * created by https://gitee.com/gin9
+ * <p>
+ * finally block should not contain return, the ide warn you as same
+ * execution sequence: expression in return then cache in stack, execution finally, return(the return on finally cover the try)
+ *
+ * @author kuangcp on 2/17/19-9:24 AM
+ */
+@Slf4j
+public class FinallyWithReturnTest {
+
+    @Test
+    public void testFinallyWithReturn() {
+        int value = doSomethingWithCoverException();
+        log.info("actual value: value={}", value);
+    }
+
+    @Test
+    public void testFinallyWithoutReturn() {
+        int value = doSomething();
+        log.info("actual value: value={}", value);
+    }
+
+    // 1. finally block will override try block return value
+    // 2. may cover Exception, if not catch corresponding exception
+    private int doSomethingWithCoverException() {
+        try {
+            return alwaysZero();
+        } finally {
+            log.info("finally block");
+            // if use return, even the compile-time exception will ignored
+            // this return will cover the return on try block
+            return 1;
+        }
+    }
+
+    // correct way
+    private int doSomething() {
+        try {
+            return alwaysZero();
+        } catch (IOException e) {
+            log.warn("catch exception ", e);
+        } finally {
+            log.info("finally block");
+        }
+        return 1;
+    }
+
+    private int alwaysZero() throws IOException {
+        log.info("invoke alwaysZero method");
+        if (ThreadLocalRandom.current().nextBoolean()) {
+            log.warn("throw Exception");
+            throw new IOException("io exception");
+        }
+
+        return 0;
+    }
+}

class/src/test/java/syntax/tryblock/FinallyWithReturnTest.java

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+package syntax.tryblock;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+
+/**
+ * created by https://gitee.com/gin9
+ * <p>
+ * try-with-resources
+ * as long as the object implements the AutoCloseable and Closeable interface
+ *
+ * @author kuangcp on 18-10-1-下午9:59
+ */
+public class TryWithResourceTest {
+
+    // primitive way
+    static String ReadFile(String file) throws IOException {
+        BufferedReader br = new BufferedReader(new FileReader(file));
+        try {
+            return br.readLine();
+        } finally {
+            br.close();
+        }
+    }
+
+    // use TWR
+    static String ReadFileWithTWR(String file) throws IOException {
+        try (BufferedReader br = new BufferedReader(new FileReader(file))) {
+            return br.readLine();
+        }
+    }
+
+}