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src/java.base/share/classes/jdk/internal/misc/VM.java

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131     // buffer memory.  This value may be changed during VM initialization if
132     // "java" is launched with "-XX:MaxDirectMemorySize=<size>".
133     //
134     // The initial value of this field is arbitrary; during JRE initialization
135     // it will be reset to the value specified on the command line, if any,
136     // otherwise to Runtime.getRuntime().maxMemory().
137     //
138     private static long directMemory = 64 * 1024 * 1024;
139 
140     // Returns the maximum amount of allocatable direct buffer memory.
141     // The directMemory variable is initialized during system initialization
142     // in the saveAndRemoveProperties method.
143     //
144     public static long maxDirectMemory() {
145         return directMemory;
146     }
147 
148     // User-controllable flag that determines if direct buffers should be page
149     // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force
150     // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned.

151     private static boolean pageAlignDirectMemory;
152 
153     // Returns {@code true} if the direct buffers should be page aligned. This
154     // variable is initialized by saveAndRemoveProperties.
155     public static boolean isDirectMemoryPageAligned() {
156         return pageAlignDirectMemory;
157     }
158 
159     private static int classFileMajorVersion;
160     private static int classFileMinorVersion;
161     private static final int PREVIEW_MINOR_VERSION = 65535;
162 
163     /**
164      * Tests if the given version is a supported {@code class}
165      * file version.
166      *
167      * A {@code class} file depends on the preview features of Java SE {@code N}
168      * if the major version is {@code N} and the minor version is 65535.
169      * This method returns {@code true} if the given version is a supported
170      * {@code class} file version regardless of whether the preview features

131     // buffer memory.  This value may be changed during VM initialization if
132     // "java" is launched with "-XX:MaxDirectMemorySize=<size>".
133     //
134     // The initial value of this field is arbitrary; during JRE initialization
135     // it will be reset to the value specified on the command line, if any,
136     // otherwise to Runtime.getRuntime().maxMemory().
137     //
138     private static long directMemory = 64 * 1024 * 1024;
139 
140     // Returns the maximum amount of allocatable direct buffer memory.
141     // The directMemory variable is initialized during system initialization
142     // in the saveAndRemoveProperties method.
143     //
144     public static long maxDirectMemory() {
145         return directMemory;
146     }
147 
148     // User-controllable flag that determines if direct buffers should be page
149     // aligned. The "-XX:+PageAlignDirectMemory" option can be used to force
150     // buffers, allocated by ByteBuffer.allocateDirect, to be page aligned.
151     @Stable
152     private static boolean pageAlignDirectMemory;
153 
154     // Returns {@code true} if the direct buffers should be page aligned. This
155     // variable is initialized by saveAndRemoveProperties.
156     public static boolean isDirectMemoryPageAligned() {
157         return pageAlignDirectMemory;
158     }
159 
160     private static int classFileMajorVersion;
161     private static int classFileMinorVersion;
162     private static final int PREVIEW_MINOR_VERSION = 65535;
163 
164     /**
165      * Tests if the given version is a supported {@code class}
166      * file version.
167      *
168      * A {@code class} file depends on the preview features of Java SE {@code N}
169      * if the major version is {@code N} and the minor version is 65535.
170      * This method returns {@code true} if the given version is a supported
171      * {@code class} file version regardless of whether the preview features
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