如何使用IDEA查看java文件编译后的字节码内容

public class StringDemo1 {

    public static void main(String[] args) {

        String str1 = "aaa" + "bbb" ;

        System.out.println(str1);

        String str2 = "ccc" ;

        str2 += "ddd" ;

        System.out.println(str2);

    }

}

//

// Source code recreated from a .class file by IntelliJ IDEA

// (powered by Fernflower decompiler)

//

package jdk.java.lang.string;

public class StringDemo1 {

    public StringDemo1() {

    }

    public static void main(String[] args) {

        String str1 = "aaabbb" ;

        System.out.println(str1);

        String str2 = "ccc" ;

        str2 = str2 + "ddd" ;

        System.out.println(str2);

    }

}

// class version 52.0 (52)

// access flags 0x21

public class jdk/java/lang/string/StringDemo1 {

  // compiled from: StringDemo1.java

  // access flags 0x1

  public <init>()V

   L0

    LINENUMBER 8 L0

    ALOAD 0

    INVOKESPECIAL java/lang/Object.<init> ()V

    RETURN

   L1

    LOCALVARIABLE this Ljdk/java/lang/string/StringDemo1; L0 L1 0

    MAXSTACK = 1

    MAXLOCALS = 1

  // access flags 0x9

  public static main([Ljava/lang/String;)V

   L0

    LINENUMBER 11 L0

    LDC "aaabbb"

    ASTORE 1

   L1

    LINENUMBER 12 L1

    GETSTATIC java/lang/System.out : Ljava/io/PrintStream;

    ALOAD 1

    INVOKEVIRTUAL java/io/PrintStream.println (Ljava/lang/String;)V

   L2

    LINENUMBER 15 L2

    LDC "ccc"

    ASTORE 2

   L3

    LINENUMBER 16 L3

    NEW java/lang/StringBuilder

    DUP

    INVOKESPECIAL java/lang/StringBuilder.<init> ()V

    ALOAD 2

    INVOKEVIRTUAL java/lang/StringBuilder.append (Ljava/lang/String;)Ljava/lang/StringBuilder;

    LDC "ddd"

    INVOKEVIRTUAL java/lang/StringBuilder.append (Ljava/lang/String;)Ljava/lang/StringBuilder;

    INVOKEVIRTUAL java/lang/StringBuilder.toString ()Ljava/lang/String;

    ASTORE 2

   L4

    LINENUMBER 17 L4

    GETSTATIC java/lang/System.out : Ljava/io/PrintStream;

    ALOAD 2

    INVOKEVIRTUAL java/io/PrintStream.println (Ljava/lang/String;)V

   L5

    LINENUMBER 18 L5

    RETURN

   L6

    LOCALVARIABLE args [Ljava/lang/String; L0 L6 0

    LOCALVARIABLE str1 Ljava/lang/String; L1 L6 1

    LOCALVARIABLE str2 Ljava/lang/String; L3 L6 2

    MAXSTACK = 2

    MAXLOCALS = 3

}