io.greptime.common.util.StringBuilderHelper Maven / Gradle / Ivy
/*
* Copyright 2023 Greptime Team
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.greptime.common.util;
/**
* Reuse {@link StringBuilder} based on {@link ThreadLocal}.
*
* Be careful that do not to nest in the same thread.
*/
public class StringBuilderHelper {
private static final int MAX_BUF_SIZE;
private static final ThreadLocal HOLDER_THREAD_LOCAL;
static {
MAX_BUF_SIZE = 1024 << 3; // 8k
HOLDER_THREAD_LOCAL = ThreadLocal.withInitial(StringBuilderHolder::new);
}
public static StringBuilder get() {
StringBuilderHolder holder = HOLDER_THREAD_LOCAL.get();
return holder.getStringBuilder();
}
private static class StringBuilderHolder {
private StringBuilder buf = new StringBuilder();
private StringBuilder getStringBuilder() {
truncate();
return this.buf;
}
private void truncate() {
if (this.buf.capacity() < MAX_BUF_SIZE) {
this.buf.setLength(0); // reuse
} else {
this.buf = new StringBuilder();
}
}
}
}