Java tutorial
package com.estool.utils.page; /* * Copyright 2008-2010 the original author or authors. * * 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. */ import java.io.Serializable; import java.util.ArrayList; import java.util.Collections; import java.util.Iterator; import java.util.List; /** * Basic {@code Page} implementation. * * @param <T> * the type of which the page consists. * @author Oliver Gierke */ public class PageImpl<T> implements Page<T>, Serializable { private static final long serialVersionUID = 867755909294344406L; private final List<T> content = new ArrayList<T>(); private final Pageable pageable; private final long total; /** * Constructor of {@code PageImpl}. * * @param content * the content of this page * @param pageable * the paging information * @param total * the total amount of items available */ public PageImpl(List<T> content, Pageable pageable, long total) { if (content != null) { this.content.addAll(content); } this.total = total; this.pageable = pageable; } /** * Creates a new {@link PageImpl} with the given content. This will result * in the created {@link Page} being identical to the entire {@link List}. * * @param content */ public PageImpl(List<T> content) { this(content, null, (null == content) ? 0 : content.size()); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#getNumber() */ public int getNumber() { return pageable == null ? 0 : pageable.getPageNumber(); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#getSize() */ public int getSize() { return pageable == null ? 0 : pageable.getPageSize(); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#getTotalPages() */ public int getTotalPages() { return getSize() == 0 ? 0 : (int) Math.ceil((double) total / (double) getSize()); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#getNumberOfElements() */ public int getNumberOfElements() { return content.size(); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#getTotalElements() */ public long getTotalElements() { return total; } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#hasPreviousPage() */ public boolean hasPreviousPage() { return getNumber() > 0; } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#isFirstPage() */ public boolean isFirstPage() { return !hasPreviousPage(); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#hasNextPage() */ public boolean hasNextPage() { return ((getNumber() + 1) * getSize()) < total; } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#isLastPage() */ public boolean isLastPage() { return !hasNextPage(); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#iterator() */ public Iterator<T> iterator() { return content.iterator(); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#asList() */ public List<T> getContent() { return Collections.unmodifiableList(content); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#hasContent() */ public boolean hasContent() { return !content.isEmpty(); } /* * (non-Javadoc) * * @see org.springframework.data.domain.Page#getSort() */ public Sort getSort() { return pageable == null ? null : pageable.getSort(); } /* * (non-Javadoc) * * @see java.lang.Object#toString() */ @Override public String toString() { String contentType = "UNKNOWN"; if (content.size() > 0) { contentType = content.get(0).getClass().getName(); } return String.format("Page %s of %d containing %s instances", getNumber(), getTotalPages(), contentType); } /* * (non-Javadoc) * * @see java.lang.Object#equals(java.lang.Object) */ @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (!(obj instanceof PageImpl<?>)) { return false; } PageImpl<?> that = (PageImpl<?>) obj; boolean totalEqual = this.total == that.total; boolean contentEqual = this.content.equals(that.content); boolean pageableEqual = this.pageable == null ? that.pageable == null : this.pageable.equals(that.pageable); return totalEqual && contentEqual && pageableEqual; } /* * (non-Javadoc) * * @see java.lang.Object#hashCode() */ @Override public int hashCode() { int result = 17; result = 31 * result + (int) (total ^ total >>> 32); result = 31 * result + (pageable == null ? 0 : pageable.hashCode()); result = 31 * result + content.hashCode(); return result; } }